The name is a bit silly but I love the story behind it.
For the uninformed: When Square was developing FF, the story goes that the company was facing bankruptcy and that this would be their last game. It ended up being a hit and the rest of history.
Supposedly and alternatively, it may have been so named as the designer’s (Hironobu Sakaguchi) last shot in the game industry and he had resolved to stop if it didn’t work.
Story wise, all different with a certain set of tropes being ever present (crystal will be a nonsense word in your head by the end). Gameplay wise, they can be samey with significant variations on progression (8 being the most out there IMHO). After 13, it does start getting much more variable with the formula.