Some of you have it right, and some others are abusing the term (confusing the meaning of the concept). It's not about skill, or about the mindset, it's about time, first and foremost. Ok, that's gonna be long.Please bear with me. Or just read the bold parts, they're supposed to be a TL;DR.
Initially, being a "casual player" is directly linked to the loose definition of the word: doing something "casually" means doing it without investing "too much", in terms of time or on a mildly-paced rhythm. The notion of casual in broader terms means "Occurring at irregular or infrequent intervals; occasional". In terms of dress-code, for instance, it means to "emphasize comfort and personal expression over presentation and uniformity".
So, formally, playing a game "casually" means without committing to a regular schedule or without trading comfort (fun, personal roleplay...) for performance, for instance. It's a notion closely related to time and norms/rules.
But consider this: most, if not all MMORPG are made so that progressing is a matter of investing time (since these games rely on players actually playing them to be profitable, it's understandable why this game design evolved as such), something which we call "grind" in a somewhat pejorative way. Simply put, a "casual" is someone who wouldn't commit to "grind" on a regular basis, that is commit to farm a dungeon X times to get a set of gear, or farm Y amount of a certain material to craft this gear or that consumable item within a certain time allotment. It's not that a casual player wouldn't do it, eventually, it's pertains more to the fact that he wouldn't commit to others to invest 20h per week to do it for next monday for instance.
Since many vertical-progression MMORPG so emphasize gear/items as a pre-requisite to even attempt certain encounters (a form of content "gating", as in "you must complete stage 1 in order to access stage 2"), then it became quite obvious to some that casual players wouldn't be able to access said encounters before some time (usually that means before the next patch for instance, when said content will become easier for some reason either voluntarily ("nerf" or deliberate easement of difficulty by the developers) or indirectly (because some gear would be either easier to get, or some other gear more powerful would become available). Typically, competitive players would consider a "casual player" someone who doesn't really care if he/she clears the content before it is nerfed, but that is already an assumption that cannot, and shouldn't, apply to all "casually playing individuals".
So that is how it then became a very loose association to link casualness with progression, since it's a consequence of the game design (yet thus doesn't apply to all games). But in real terms, it doesn't take into account the skill of so-called "casual players" (which, given the proper gear, could be able to win these encounters). To link casualness with progression is not a very valid use of the term, it's more of a consequence of game designs.
There is however the matter of training and learning which comes into factor, reinforcing the premise that casualness is linked to a somewhat lesser skill. It isn't true in itself, but then again consider this: most MMORPG (and games in general for that matter) are procedural events that need to be learned, often by heart, and practiced, often a lot, to be mastered by a player. The more you do something, the better you get at it; the more you fight a boss, the better you are at responding to its moves and making good choices throughout the fight. Thus it became relatively easy to imply that casual players don't have the same "skill" as hardcore players do, because it's simply a matter of practical training on specific encounters. As any generality it's bound to be wrong at some point, because not everyone learns at the same pace, and some players are just better/worse than others, but as any generality, there's some statistical truth to it.
The same can be said about teamplay: it's obvious with professional sports players and teams, for instance, that the more they play together, the better they get at coordination and reading or anticipating others' moves, and that it would be nearly impossible to win high level competitions without some serious training together first and foremost, both between and during matches (first-timers in a sports competition finals are usually at a statistical disadvantage compared to seasoned teams, because stress and a lot of other factors then come to explain statistical differences). Statistics, however, are by no means a prediction of the future, and fighting against the odds may be one of the most enjoyable experience in life, especially when there's a real chance to win —in gaming, you often see some casual players very opinionated on that fact. But beyond that, fighting against too many odds is just bound to be frustrating, and that might explain why some so-called "elitist" players refuse to try to play too much against the odds, because they know that it's a 1 in 100 chance to win.
All these terms, "casual", "elitist", "hardcore" are very relative, subjective even, and remember: you're always someone's jerk, you're always someone's casual, you're always someone's elitist. But then one sees how "casual" became a loose term for "bad player", "no skill", and all sorts of abuse. It became a downright insult in some communities (admittedly less so as games evolved to be more tailored to casuals indeed, notwithstanding a strong dose of resentment by some competitive players in need of recognition). Objectively, it's not because someone plays a game casually that this person isn't good at it, and insofar as any mastering requires a bit of training, brains and experience in other games are always good factors making up for a somewhat lesser implication in any given game, let alone patch (implying you have previous experience in this game). Personal skill doesn't create gear, it doesn't negate content gating, but it certainly goes a long way, as cooperative mindsets do in teamplay. Casuals can thrive in some games, provided the design suits that gaming style.
The term "hardcore" is supposed to be the opposite of "casual", meaning that "hardcore players" invest a lot of time in a given game; and that consequently results in overall better skill statistically, since humans are machines of habits, of neural reinforcement (both logically and in terms of psycho-motricity). But it doesn't account for the fact that not all humans are equal, once again, and that concentration/focus for one, or past experience, will always come into play at some point. I'd easily wager that a team of hardcore kids may lose against a more casual team of experienced adults who've "been there, done that", since you don't bridge a decade of experience simply by putting 50 hours into a game for a few months. It's just that, admittedly biologically, our reflexes may begin to wan after 25 years old or so, but then it all depends on which game genre you're competing.
A good example is a top-guild on WoW and other games (I think it's "Method" but I might be wrong, can't recall the name for sure) who makes a point of raiding only 3 times a week but in a very competitive mindset, and they indeed achieve as much as others raiding 5, 6 or even 7 times a week during the same timeframe (first downs and so on). It's a perfect illustration that time invested, in itself, isn't the only factor determining success. Some MMORPG allow for talent and coordination (teamplay) to shine, and some individuals are just better at that than others. I personally think that FF XIV requires both: gear (there are checks, indeed, in terms of DPS on Amdapor boss#2 or on Garuda for instance, or in terms of HP on Titan) and skill (some bosses moves just ignore gear and require plain and simple skill to be overcome as in Bahamut Coil 5).
So yeah, casual in itself is just about how much time you invest in a game, how regularly this time is scheduled in the week. But defining players "categories", if it means anything, cannot be reduced to such a narrow view as "casual" or "hardcore". These terms have come to bear way too much meaning for their own sake, and in the end don't mean anything much beyond their strict definition (a relative one, mind you). This is why labelling is just plain and simply refused by many, and legitimately so. Yet, granted, even two nights a week in a very "competitive" or "military" mindset isn't very casual anymore, which prompted the term "softcore" or "semi-hardcore" (hardcore in the mindset but less so in time invested).
Currently, as far as I know, the consensual standard is that you're casual if you play less than 10 hours a week and on an irregular schedule, you're "softcore" or "semi-hardcore" if you play 10 hours or more and/or on a regular schedule (3 hours a night for two or three nights, usually from 8pm to 11pm, depending on your country's scheduling habits), and you're hardcore above that (more than 20 hours or more than three nights on a scheduled basis). Three nights a week is really the threshold making you clearly pass from one world to another in a lot of players' perception, and it seems that many raids are designed around that threshold (typical 10-boss instance with a weekly reset, it takes a minimum amount of time to try and later on complete every week).
Coincidentally, investing more than 10 hours a week in any non-professional activity is indeed pretty much hardcore, be it sports or any hobby. You're probably ripe for amateur competition at that level of investment, provided you do it a bit seriously. In games, competition isn't usually formalised as in associative real-world sports, but admittedly, it's not very casual to do, on average, 2 hours or more of an activity every day of the year. It makes you quite "into" that thing. That's "softcore" already
The fact is, in MMO, most raiding players associations (guilds, free companies, whatever) will require a player to be present at least once or twice a week (8-11pm) if that player wants to participate in raids (since they involve many people, a bit of organisation is required, or else nothing ever gets done), and from that moment on, in my opinion, these players are already too much invested in a game to be called "casual" —since, of course, these raiding nights are not all they will be doing in the game, there's bound to be some extra time around the fixed schedule, easily putting them above the 15-20 hours mark a week.
My (long, sorry) 2 cts on the question.![]()