I never used to be a character fan. Although one of my best friends always has been and I didn't really get it for a long time either.
But I was a show/performer fan. I came from Mad T fandom, where we were fans of the singers and musicians there. That led me into a fandom for the entertainment team as a whole to all the singers, dancers, musicians at the parks.
When T ended, I wasn't sure what to do with myself as the park was cutting back the shows and the performers weren't around as much. I honestly wondered if it was time to give up the parks on the regular basis I'd been going.
But then Marvel came to DCA - first with a show - the Guardians of the Galaxy Awesome Dance-Off. This coincided with my fandom for Marvel/MCU in general. And it had performers who were also characters. And then they brought in Marvel characters to the Hollywood Backlot. Again, I wasn't fully engaged. But then they brought in my favorite Marvel characters to the Hollywood Backlot and suddenly I found A) it was fun to visit with my favorite characters and engage with them within their storytelling universe and B) the level of acting and improv these character performers have to do is every bit as difficult and legit as the singers and performers in the shows around the park. Conclusion for me: IT'S ALL ENTERTAINMENT. And I happily fell into character fandom - mostly with face characters since I can talk with them, but I've gained some affection for fur as well. But I'm a face fan, first and foremost, because what they do is difficult, it's performing, and just as in the shows, there are different levels of ability, but some are truly stellar.
Let me give you an example - here is Thor randomly doing a SEVEN MINUTE IMPROV MONOLOGUE without hesitation.
And if you can't appreciate the skill it takes to do that and the thought put into character development and representation, and chalk it up to someone being just "a Cal State Fullerton student in costume", well...
So in combining my appreciation for performance with my appreciation for cast members with my fandom of Marvel especially, but also Disney, Pixar and Star Wars as well, I became a massive character fan and engaging with them has provided some of the greatest moments in the parks for me ever.
It's not a childlike suspension of belief for me - though there are moments of that - it's LARPing in a favorite fan universe with awesome lovely people - the character cast.
So that's how and why I appreciate character interactions as an adult guest.
But my friend still just loves to hug the fur and enjoys the challenge of meeting as many new characters as possible - and I respect that, too, and understand it a little more now.