I run a pihole and see basically the same thing you do. I think the stuff that’s left is built in, hosted on their own domain. If that’s the case, probably not blockable across the board.

With a quick search I found an extension called ‘block “read more”’, but it’s 2 star with 2 users so… idk maybe there are better ones but it looks like that extension had to be done for each website, rather than universally, so it’s a very small list.

If you don’t mind doing a bit of work for it, and the complaint stems from the same set of websites, there’s an extension called element blocker that lets you block whatever you want from a given website, like chat popups and stuff.