Be there trolls in this here thread??? Best not feed them, I suppose...
Returning player here. Started in early 2005, been on-again off-again ever since.
Testimony of someone who has never had a character above level 40, and just started fresh with a new account and a new server:
1 - Is it too late to join?
I haven't had any problem whatsoever finding parties. Maybe I've been getting lucky, but I've only been back for 3 days and I've already got one job up to 19 and another up to 15. This game is still very playable and there are still a good number of active people. My advice to make your FFXI life much easier - look for a good linkshell! You're going to want a friendly social LS to start. Example: GreatBigSea
of CaitSith. I joined CaitSith exclusively because this LS seemed to be helpful and friendly, and I don't regret my decision =) Also, you can ask around when you get in the game after you've picked your server. Though there are exceptions, most of the playerbase are very friendly and helpful, and probably know good social linkshells to recommend. The server forums here are a good place to inquire about linkshells that are accepting new players.
You will NOT enjoy this game if you do not attempt to reach out to others and network yourself. This includes joining linkshells, making friends through parties, helping others (believe me, those newbies grow up fast, and they'll remember all the nice things you did for them), and being involved.
2 - How does this game differ from <insert name of MMO here>
Community. Intricate story arcs. Focus on PvE. The absolute necessity for you to socialize - if you don't, you aren't going to get very far.
8 - Is FFXI dying?
Servers still have a healthy population, as far as I can tell, and you can expect that on each server there will be anywhere from 1.8k to 2.5k people online at any given time. With FFXIV coming out, it seems like some endgame 75s have left, but in my opinion this has little bearing on anyone who is coming into the game as a new or returning player. Those 75s that are awaiting the FFXIV were probably only doing endgame content anyway, it's not like you would have ran across them in Valkurm Dunes.
I've seen new people every day so far, and that's on CaitSith alone. As long as new players continue to come into the game, it won't be dying. Even after FFXIV comes out, there will still be people who play this game, much like after EQ2 came out there were still people who only played EQ.
So, if you've tried the game out, and you like it, don't let these things worry you. There's enough content here to keep you busy (and enjoying it) for a long time, and plenty of players around to enjoy it with. As it has been pointed out here already, this game isn't for everyone. If you like being a lone wolf, this game will be off-putting. If you dislike working in teams or helping others, this game will be frustrating for you.
And if you decided to join CaitSith, feel free to drop me a line. I am more than happy to help.