I'm 50/50 on the subject of fanservice. While I do prefer more original things it's nice that the devs put in the effort of bringing in older/current SE franchises into the world of Eoreza.

On the Ivalice raids, I disagree to a degree. I played nearly all of the final fantasy titles as it's one of my favorite series. So seeing them add Ivalice was great because that universe is one of the best Squaresoft/SE has created.

For Omega, I felt that it was a good mix of nostalgia and originality. I liked seeing all of the bosses from other games while having a decent reason for them showing up. Also the story of Omega is original plot-wise. It's one of my favorite raid series tbh.

Overall, I think there's a hard balance for them to deal with. I think it's nice for them to bring in other games to bring hype and give fanservice to the fans that have enjoyed it. I do understand more original content is good Ofc. Nier was pretty hype tbh but so far the writing of the Nier universe is far too complicated to be out into a 3-part alliance raid, it would have been as a long term event/side quest chain.