I've long settled on interpreting the meaning of upvotes as "I like this post and want to see more like this".

I agree, though I still intuitively get "This post was worth more points" or "97 points? it was only as good as this other post, which has 30 points".

So it kind of puzzles me why you ... expect that your own evaluation of a post should be a good indicator of how others like it.

Really? That seems like a completely natural expectation to me. Like, I like strawberries dipped in chocolate, so I would assume (with no other info) that a random person would like strawberries dipped in chocolate. We are far more alike than not.