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.
It does feel like there a a significant level of friction with each of these equivalent platforms though, including Lemmy. As with anything new it’ll take time to catch on but each layer of complexity will be another stopping point for non-tech people.