I really didn't like how uninspired a lot of the stages were in Ultimate. New Donk City Hall is a somewhat bland way to depict the location; Dracula's Castle was great but it was like, the obvious way to represent a CV stage; Spiral Mountain is a pretty obvious stage, and not as cool as Click Clock Woods would have been; Great Plateau Tower is super boring and too safe; etc.
The stages just seem really afraid of doing something unexpected. The only stage that surprised me was Mementos, and that's because of how it was done. Mementos is kind of the "obvious" choice, a recurring area of Persona 5. Imagine if we got New Donk City Festival, or if we got a Divine Beast, or if we got Clock Tower instead of Dracula's Castle. I bet if Sakurai went into Melee with the mindset he has today, we would have gotten Clock Town or Termina Field over Great Bay.