Would you prefer "self-sabotaging"? "Lacking consideration of others' time"? Being new to X content is one thing, being rusty another, and getting PKed something further still, but if you consistently can't even combo appropriately or use CDs by level 80, it's almost always going to be some shade of one of those three. Again, the key here is basic competency by the latest in basic content (e.g. level 80 dungeons), the beginnings specialized competency in the beginnings of specialized content (e.g. level 80 Savage), and a fair bit of specialized competency by the time you join a E4S farm group, for instance.
"Be (relatively) prepared," for short.
The bar isn't high here. If I can perform just fine through mouse-based movement and button-clicking alone while text-chatting with my FC and talking with my roommate and my party being none the wiser to it, it takes some manner of laziness or intentional underperformance to be unable to perform even half that well.
That could be an unwillingness to deal with whatever inhibitions you have that dissuade you from testing yourself through learning (self-sabotaging). That could be an unwillingness to spend effort on principle "because it's just a game" (lacking consideration / laziness). That can be a desire to prioritize other things, and believing that engaging fully with performance means you must be losing out elsewhere (lacking consideration / self-sabotaging). It can be a twisted logic that tells you that if you go fast, you'd be "disrespecting" the content (self-sabotaging). Whatever. But all of that stems from being unwilling to fully engage with what's happening or improve one's performance. Sure, we could break down the minutia, but the labels are generally accurate, even if not superfluously precise.
a) Then you deny the majority of players a useful self-improvement tool. Believe it or not, we casual players like knowing things, too.
b) That's fair. And one can always do both.