Actually no, you don’t get BP for building. I tried. You get BP for various forms of grind, like resource collection and killing mobs, and passively by having benches produce stuff, which is what I did. Also, no (discernible) BP for just staying logged in either.

Most people I know do the BP in SP anyway, but that may indeed not be the majority of players.

Like unfinished releases (Cities Skylines 2) and same-same slop (whatever the current CoD is). Seems to be going well, all told.

I agree though, the challenges still are too specific. Broader categories (demonic enemy, giant enemy ect) work well, but super-specific ones without a guaranteed spawn (demonic hyeena, storm beast) are just annoying, as you cannot just spawn them in anymore.