Other than that, all of these things are things people can build using the API. I agree they're needed, and I think enough others do that things will get built.
I certainly want to build my own algorithmic feed, because reverse chronology is already a nuisance to me.
Other than that I think what you're describing might well be a good feature for one of the frontends to support. Incidentally, since all of the profile info is available without auth, it's also possible to build an entirely separate profile browser that could offer that filtering for any profile.
EDIT: Mastodon in fact includes a profile browser for remote profiles; it's just that when logged out it will redirect to the remote profile instead of show the "local view" of it. So if someone wants to build a profile browser like that, all the necessary code for a good starting point is there in Mastodon already. Thought it might well be easier just to do it from scratch.
without those things, it's easier to just run out of stuff and people to see, and end up in a place where you're caught up with things, and new people aren't entering your circle, and the activity just stops. well, it is also unlikely, because people just do stuff and mix other people in, but it's easier to end up in that static state, when you don't get suggestions in other ways.
at least there are reblogs. but there's also no option to filter those out right in someone's profile. so it's gonna get real annoying if those are gonna be the only way for someone to push content from somebody else.