It’s especially handy if you read a bunch of, say, NYT feeds as they cross post a lot. In fact I read my feeds almost exclusively using these topic filters, and only at the end look at the remaining unread. I have topic-selective “feeds” like the Ukraine war, climate change, etc.
I have a huge “Junk” filter (podcasts, stories about movies, other crud I don’t want) that I scan first and mass-mark-as-read. That way I could quickly scan down the list, read any I wanted to (few - they were mostly the same) and then mark all as read with a couple of keystrokes. So, example when news about the Queen flooded my feeds, I made “smart feed” (in ReadKit) that matched `not read & (“title contains Queen” || “title contains Royal” …)` similar to a “smart mailbox” in apple mail, and using the mac’s system widget for generating such filters.