Quoting Manu Moreale
Look, I get it. You want to bring people on your own site where you can control the design, the look and feel and quite possibly try to nudge them towards a book you're selling or a course or whatever. I get it. But the entire point of having an RSS feed is to prevent me from having to actually go to your site to read what you wrote. RSS is not a notification system. It's a distribution system. Distribution of content. I don't want a notification. I want to read your content. Which is why I subscribed to your RSS feed in the first place. So stop with this nonsense of only serving an excerpt in your RSS feed.
I agree with Manu. I use RSS so that I don't have to visit websites to read the web. I use Feedbin for RSS and Reeder for reading. One of the great features of Reeder is that if a particular feed only serves excerpts, like say 9to5 Mac, Reeder has a reader mode that displays the full text of the article within the app.