FFXIV is the wrong place to find people to bring over to FFXI; for the most part, anyone there who would enjoy FFXI played it before FFXIV was launched, and either already plays both or moved on to the shiny newer game. Having a discounted subscription option for FFXIV players could bring some back, maybe, but I can't imagine it would be a lot. It probably wouldn't move many FFXI players over to FFXIV, either, that ship sailed decades ago; ultimately there just isn't that much to gain from doing it.

Now, if you know anyone playing Runescape or Everquest, you might find converts there. World of Warcraft, maybe, but if they like the gameplay there they'd like FFXIV more.

But yeah, that does seem to be where we are, doesn't it. There might be more players if there were more investment, but why invest if there aren't many players, and maybe the game would be an easier sell if it were more modernized but why invest in modernizing a game that very few people are playing? This is why there's so much discussion of a remake, and also why we all know deep down it's never happening. Unless someone can figure out how to drop Cloud Strife into the middle of Ru'Lude Gardens, anyway.