For me personally, factors that I find important are:

• Either no ads, or otherwise ads should at least be clearly distinguishable as such, instead of blending in as ordinary posts (this happens on Instagram to such a degree that I find it quite annoying);

• The same as for ads, above, but for posts by accounts that I'm not following;

• The ability to have strict time-based ordering of posts.

(I'm curious about Bluesky and if it's worth trying to get an invitation to it.)