No one should like that game.
By every single reasonable metric, it fails as both a piece of art and entertainment.
Final Fantasy XI is primitive and slow, and those were two of its best qualities. Even diehard fans cannot mince words on this. And it's not just the sluggish combat, either. Everything takes forever. Before acquiring a chocobo license, airship pass, or Teleport spells, it can take you 30-40 minutes to run from one place to another on foot -- and that's if you're avoiding combat and not regularly getting jumped by orcs, goblins, yagudo, or quadavs. You have to wait for shops to open, wait for the best in-game day to craft items, and wait for people to buy your swag at the auction house. You sit around and wait for you HP/MP to recover when you hit the "heal" command, you wait for people to invite you into their parties, you wait for your party members to run off and get Signet, you wait for somebody to come and cast Raise on you when you die, you wait two hours to use your special ability again, you wait one hour (in real time) between the five feedings in the chocobo license subquest. Roughly 75% of the Final Fantasy XI experience is waiting for the Final Fantasy XI experience.
I fully understand that some people love game like this. They love a game that requires time, patience, and dedication in order to accomplish things. Some people even enjoy the game's leisurely (now I'm mincing words) pace, as it makes Vana'diel more realistic and immersive.
The problem in Final Fantasy XI's case is that none of this is actually fun. During your stay in Vana'diel, you are constantly level grinding, crystal harvesting, doing NPCs' fetch quests, and spawn camping like you're on somebody's imaginary payroll. As I mentioned above, you have to take the same approach to Final Fantasy XI as you would a personal project such as building a model ship in a bottle, taking a martial arts class, or writing a novel. It is an arduous, time-devouring, and often frustrating process.
Exploring Vana'diel is a thrilling experience. Indeed. On the rare occasions you're actually exploring, anyway. Most of the time, you're spawn camping and level grinding on the same map for hours on end. Depending on how often you play and how much focused time you spend on leveling up and keeping your character's equipment and spells up to date, it can be anywhere from a few days to a few weeks before your character can cross over into a new zone without fearing swift evisceration at the hands of the first gob you encounter. Until then, you're stuck running back and forth between your home point and the local EXP party hotspot until you put in enough time to become sufficiently leveled up to move on -- on to the next EXP party hotspot.
Final Fantasy XI's battle dynamic is structured such that every individual player is a limb of the greater organism in the party. Watching the party's various skills efficiently mesh together to blast a mob to hell is definitely a sight to behold. Actually being a participant in that process is like working a post at a factory conveyor belt. You're doing the same thing, standing in the same spots, hitting the same macro keys over and over and over again, until the monster dies or otherwise turns the tables and kills everyone. The game isn't designed to let you do anything else. The engagement strategy never changes.
Is the game an entertaining diversion? No, not really -- it's too great a time devourer. It's not a game you can hop on and play for an hour or so at night before dinner. There is no point in playing for an hour. An hour is how long it takes to log on, check your Mog House delivery box, peruse the auction house, hit up a special NPC to cast Signet on you, start or join a party, and walk halfway to wherever you're trying to go. If you can only play Final Fantasy XI for an hour at a time, you're better off not playing at all. Are the battle and character customization systems what carry the game? Not really -- combat is slower than molasses, and the Job/Subjob setup is a drag, especially in light of how many hoops the game expects you to jump though in order to unlock new jobs and level them up to the point at which they become viable. Does it give its player any new ideas to think about? No -- unless we're talking about how it might inadvertently trigger OH MY GOD IS THIS ALL THERE IS TO LIFE existential crises in frequent players. Does sitting alone and entering a level-grinding trance night after night for a period of months or years enrich your life in any way? No. It does not.
Final Fantasy XI is a useless game. If our lawmakers wanted to be consistent, they'd outlaw video games like that on the same professed grounds as marijuana prohibition. Chronic use of Final Fantasy XI will make you dull, reclusive, unmotivated, unthoughtful, and detached from reality -- and unlike cannabis, it isn't even fun. And that, for a video game, is the greatest crime of all.