In communities where I’m a regular user, I mostly judge by title and category.
In my “home community” where I’m a moderator, I read, or at least skim through, probably about 60-80% of the topics. When I skip topics, it is usually because a) I have checked the topic recently, but it’s neither particularly interesting to me nor an overly heated discussion, or b) it’s from one of the categories with a lot of small talk content.
Unfortunately, I don’t think AI summaries would help a lot with either case. For me, they basically only come into play, if I am starting to read a very long topic with a lot of posts, or if the posts themselves are quite long.