Except now your readers have to click out of the RSS reader, rather than stay in there and read. I find it jarring and obtrusive to do that, and prefer just to visit the site instead if they RSS did this.
I usually prefer that as well, but if the choice is no RSS and headline+excerpt RSS, I’m absolutely fine with the latter. Without RSS I won’t read any regular content.
Most readers embed a browser making this pretty simple.
I prefer content embedded in my reader, but I don’t mind clicking through if it helps the author. Though, in my case I doubt it will since I’m blocking any kind of trackers, which includes many ads.