You have to first determine whether or not you might want to merge it...

Having not reviewed it, how do you know you are never going to merge?

If a PR claims to solve a problem that I don't need, then I can skip its review because I'll never merge it.

I don't think every PR needs reviewing. Some PRs we can ignore just by taking a quick look at what the PR claims to do. This only requires a quick glance, not a PR review.

I took this thread as asking whether PRs that are pulled in should be reviewed.