I think the main difference here is that the families that have been to "potter land" have already been, and opening another ride under the same IP will have diminished returns, regardless how popular.
Harry Potter is also an aging IP, unlike Star Wars which has a new film release every year, and seems to be more popular than ever. I don't think Fantastic Beasts was the big hit they were expecting either.
Magic kingdom doesn't need Tron to attract insane crowds. Avatar will be old news by the time these open.
I think Nintendo land has the real chance of bringing a lot more families, especially considering the popularity of the switch.
Now if UOR ever gets that iron man flying coaster off the ground, then we are talking.