Boxing has an older fan base, no doubt about that imo.
In general, I would say boxing fans are more knowledgeable about boxing than MMA fans are about MMA. I don’t proclaim to be an expert on all aspects of MMA, but if I use this forum as a barometer compared to a boxing forum I post on, there are more people here who are very easily identifiable as people who have not only never been in a legit fight gym, but have in all likelihood never played any sport competitively.
Hindsight bias is a great thing, but it wasn’t too long ago that the MMA community were convinced that Rousey was a ‘once ever’ athlete and that McGregor would KO Floyd Mayweather in the ring. The younger fan base are a bit less cynical than the older boxing fans I feel, and when you’ve got the massive UFC hype/marketing machine underpinning practically everything the sport does, it’s easy to see why every big thing that happens is greeted with a lot of hyperbole. It’s good in some ways because it allows the UFC to build a star at a pace that you simply couldn’t in boxing, but those same stars fall so quickly.