XI wouldnt work today ebcause the demographics for MMO are 20-30 year olds. Back when MMO were fairly in the late 90's and early 20's most games were young teenagers who had time to devote 10 hours a day. It wasn't until WoW came out that MMOs began to standardize certain things like a Duty Finder to matchmake players across servers into an instanced battle, as opposed to shouting in towns to assemble a group, manually. The pros of this are instanced content, which is fun the first 2-3 times you do it.
In FFXIV, you queue up, it takes ~1-30 min to get players and then you instantly teleport to the content and begin.
In FFXI you had to assemble a group of 6-18 people manually, which could take hours. You had to double check with EVERYONE that they: 1) have necessary pre-reqs to enter the battle, e.g. are up to or previously beaten it, have the entrance key item, are above the level, etc. During this time, players often left/disbanded because it took forever to form. Once you finally form a group, you had to all manually get to the battlefield entrance. Often times these were DEEP inside a beastmen's dungeon, which could be 5-7 floors high (or deep) with mobs that aggro. Hell, just getting to the dungeon itself was a pain as you had to teleport to the nearest zone (often 3-4 zones away from the target zone), then walk or ride a chocobo to the dungeon. You couldn't take your chocobo into the dungeon because the dungeon was a separate area. You then use items or magic to cast Invisible/Sneak (to prevent aggro from adds, which chased you forever, unlike in XIV where they give up after a certain distance). After getting to the battlefield entrance, you had to all enter simultaneously. After all entering the instanced fight, if anyone attacks before other members are fully in, the ones outside trying to enter are locked out. Problem is, for sidequest/special battles that drop loot (as opposed to MSQ battles) you needed some kind of key item to enter, which is lost upon entry. If you die/wipe you lose this item and need to get new one (not always easy, some of them require gil or a quest or drop to acquire, or are given once every 2-3 days EARTH TIME). Fine--you're in the fight, but people die and you need to retry. Too bad though, because in XI if you all wipe, you get instantly booted from the content and all entry items lost. If players have Re-raise cast on them before, they can attempt to raise up. If they died too close to the boss, the boss might re-aggro you since you raise where you stand. If 3 or 4 people raise in safety but one person raises too close, the boss aggroes EVERYONE and re-kills you before you can get a chance to cast Raise on everyone. But let's say you managed to raise up after a wipe and try to reset. Weakness in FFXI is -90% HP and +100% slow for 5 minutes. Also every death removes 10% of your EXP toeards next level. When level capped, if you die enough, you can de-level.
Moreover, if you de-leveled from 75(highest cap for many years) to 74, all your gear that's only wearable at 75, can't be worn (imagine deleveling from 70 to 69 in the middle of fighting a primal and all your ilvl shit is de-equipped). All your abilities are still on cooldown and FFXI cooldowns are 3-10 minute each. Not even mentioning the SP abilities (which are quite powerful but with 2 hour cooldowns). Many special battles that dropped loot required tactical use of these SP abilities (similar to LBs in XIV). If you used them on your first try and wiped, good luck winning without them. Did I mention most battles had a 30min time limit, some of which took 15-20 minutes? If you wiped and somehow managed to reraise and come off weakness, you were fighting the clock. Also if you died during combat and raised, you are OUT OF COMISSION for 5 minutes. You know how in XIV if you die and are raised, you can get healed up and keep fighting, albeit, with lower DPS? In XI, when you raised, you had 5 minutes of -90% MAX HP, and DOUBLE auto attack delay (you needed auto attacks to gain TP to use weapon skills, sort of the inverse's system of XIV). So instead of swinging once every 5 seconds and getting 10 TP, you swung once every 10 seconds, and you needed 100 TP to do any weapon skill.