* No pagination, and in practice it's very inconsistent how many recent posts are included. This makes the feeds only useful for new things, not as an archive.
* I don't actually want the full post content in the main feed, a description for every item would suffice. For a blog like WaitButWhy, the RSS XML is huge.
For your second gripe, perhaps a separate "excerpts" feed would do it. I know some podcasters publish the same content over multiple feeds for this kind of customization.
That being said, for some reason that escapes me, some news sites don't make it easy to see a list of articles at all (looking at you, https://cbc.ca/news). And when writing this comment, I see that if you scroll down far enough you can see more articles in this really annoying tile format (the app is better but I hate downloading a ~300 MB app when a <10 MB RSS reader is all I really want).
TL;DR: somehow it isn't just RSS but even somewhat publicly funded news sources seem to prey with the "get you stuck in an endless cycle of scrolling while you're trying to find the content you want" trap.