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.
15-year reddit veteran here. Spez thinks us old-timers are freeloaders for continuing to prefer old.reddit and the third-party apps. The truth is, that site is dead and what Lemmy offers now is closer to that original vision than current reddit ever will be. Reddit is Dead. Long live Lemmy.