This is because characters that have been portrayed as humans not in suits in films are never that interesting because suspension of disbelief is harder—even for kids. Chewbacca is a man in a Chewbacca suit. Same with Kylo Ren or Vader. But the Rey walking around is not Rey and everyone can see that except the youngest of children.
The fact that you put this on the popularity of the movies or character instead of this palpable difference suggests to me that you are not thinking through this clearly. Kylo Ren is quite a bit more “popular” and evokes far more reaction in the parks. He is from the sequel trilogy and yet you can suspend disbelief that it is actually him. Much harder with Rey.
Try this thought experiment—would anyone give a crap about actors dressed up as Han, Luke, or Leia walking around? No, they wouldn’t. Case closed. It’s not about the movies.