The smaller overall population makes a pretty big difference in the feel. I think it would be quite a long time before population comes close to corporate platforms (The Fediverse covers all styles of social media). That being the case it should feel smaller and more homey for some time.
It's possible there is some filtration of the user base since there's more involved in getting on the Fediverse. Or it could be a different kind of user attracted to it to begin with. In any case I agree there's a better class of posts here.
The lack of advertising makes a big difference in the cleanliness of the interface. That's not going to change and the design will only improve over time. This is polar opposite of corporate entities where the interface tends to get more cluttered over time with ads and feature bloat.