As quoted from the linked post.
It looks like you’re part of one of our experiments. The logged-in mobile web experience is currently unavailable for a portion of users. To access the site you can log on via desktop, the mobile apps, or wait for the experiment to conclude.
This is separate from the API issue. This will actually BLOCK you from even viewing reddit on your phone without using the official app.
Archive.org link in case the post is removed.
Lots of rotten social platforms do this. If you’re browsing on mobile, they’ll dumb down the experience or intentionally make the design painful, in order to bully you into using the app.
It’s gross, and as a software engineer, I find it an appalling practice that is anti-user.