In true SE style, the installation and account creation is an absolute mess. It is for FFXIV:ARR/HW as well.
But once you get past that, and if you can look past the 2003-era graphics, it is an FF MMO as it was meant to be. If you find that XIV is too easy for you — legit complaint, since most hardcore raiders have Alexander (Creator) Savage on farm with 4 months to go until Stormblood is out — then maybe the no-hand-holding, butt-spanking brutality of XI might be right up your street.
XIV gives you an essay and a map. XI gives you a set of coordinates and a pat on the bum. Best pray you’ve bought the map for the right area, and you don’t aggro some random mob 20 levels above you on the way. Final fantasy XI is a 15 year old game that is as strongest as it is when it started and if you are thinking of giving it a go you will be happy.
I am actually surprised by the amount of enjoyment I get from this game. I picked it up just to try out and experience all of final fantasy main installment games, but it pleasantly surprised me for such an old game. I like retro games though, so you should take it with a grain of salt.