I think you'll find that after ten years of trying to get Microsoft to drop the Game Pass requirement, Square finally gave in and made this deal.
Back in the day, they did a deal for FFXI Online on the Xbox360, you could get a free silver membership to bypass the Gold (paid), but not here.
It is unfortunate, but you could still play with your current character by purchasing the PC/Mac/Steam/PS4/5 version if you have access to one or more of those platforms.
Really depends on how much you use your Xbox, but if you don't use it much, you could always pawn it and get a PS5 or gaming laptop/PC good enough to play modern games.
Just saying, as they won't drop the Game Pass requirement.