For me personally, where I see endorsements as most relevant is for races where there are either multiple candidates who are (or purport to be) the same party, or where parties aren’t specified. For those races, if I see a bunch of local Democrats all endorsing the same candidate, I can be confident that that one’s probably the real Democrat.
It’s also relevant where there’s some particular expertise. For instance, for school board elections, I look for the endorsement of the teachers’ union, because I want a school board that’s good for teachers, and the union is the best-qualified entity for determining what that is.