There are a lot of feeds now with titles and maybe a short paragraph of text, like the beginning of the article or a summary.
There is a world of difference between sites maintaining those feeds vs. nothing at all. Having a signal that an article is there with even the slightest amount of context is so much better than the alternative.
It's mildly annoying to visit a site for the full text (with your ad blocker), but signing up for newsletters etc. from each site one-by-one is really painful.
If I'm going to take 5+ minutes to really read something, it's OK to visit the site. That means something is interesting or relevant enough to invest my time in. That signal can usually be gleaned from a title and short paragraph. Compared to the number of new things published every day, it's relatively rare to find things worth those 5+ minutes.
From what I can gather, many people use RSS readers to follow 5-10 feeds, and they slowly look through and read most of the articles. It serves as a convenient way to follow their top few sites and maybe a few aggregators like HN. Other people track 100s of feeds and quickly scan what's happening, only diving into something if it's interesting or important.
I'm building a service for the second type of person (mainly because I'm that type of person, TBH). No idea what the ratio of "completionists" vs. "scanners" is. Having title-only feeds is not ideal for the latter group, but it's usually fine.