I would argue Simu Liu is someone we like in real life. We just don't know him, and he hasn't shown up in anything since his movie came out two years ago and we have no idea when we'll see him again. And Captain Marvel hasn't been around since Endgame four years ago. In the early days, since they didn't have as many characters in the MCU, you didn't go as long between their appearances. When they were really diving into getting us to know the early Avengers, we didn't go nearly as long between seeing them. But they're doing so many characters now, there's a lot longer between them, and we get bored.
That and, in all honesty, the freshness of those early years of the superhero explosion have worn off. They capitalized with a lot of content while they could, and they pumped out a lot of good to great stuff for a while. Everything hit, so we were excited for the next installment. But after a few good to meh to bad offerings mixed in between the good stuff, the audience isn't as psyched to see every last piece of the MCU.