It took me about a week to be high enough level to play with parties. But that was with using stealth and perseverance and not being too gung ho and trying to kill so many ITs in a row. Although with it being a game that is meant to be played with others, it really can seem to be slow and tedious trying to grind levels by yourself.
Even when you start playing in groups it can be even harder to test your patience because you have to accomodate with other people, but funnily enough, that was part of the reason why I liked it. I'm sure that anyone who's been on a sport's team or something would know what I mean. I know that most mmorpg has some aspect of teamwork, but those who have played XI would know that only a few jobs and oddball main/sub job combinations can solo. Even then, most people solo to do something different not because it's more efficient.
Though sadly, of course it can't be for everyone. And it's not like long level grinding is new in FF. And plus with it being a subscription paid online game they have to tweak it in any way they can to make players play longer. But even aside from all of that, if all you can think about is getting to some level as fast as you can and thinking about how much time you've wasted when you delevel, when there are a lot of other things to do, then you probably won't enjoy it as much. I never really cared that much about dying and losing exp until I was in my 60's, because if you play with friends, not nearly as much seems tedious and boring. And yeah... I think what really distinguishes a mmorpg is that it lets you play with others so that your experience will be a lot more fun.