Didn't Yoshi state from the very beginning that the game is going to be a theme park with different FF stuff (and now others) thrown into it? Besides, you're a little late to the party considering we already had the actual Noctis, Lightning, and Iroha show up from their own games and Iroha is now canonically stuck in our world after that event.

This game has been mixing with others from the very beginning and the Ivalice stuff was pretty light considering none of those characters came over in a portal. Our Rabanastre is not the same one in the Ivalice Alliance series and does not share the same history. Dalmasca was already mentioned all the way back in ARR with the conscript we bump into and we go inside the FF3 Crystal Tower, so this game was built upon taking parts of other games for content whether you like it or not.