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.
They already made the mobile site practically unusable by constantly reminding you to use the app. The mobile browsing experience was just terrible. They can just show the same adds in the mobile browser…
Ironically, I’d just set my browser to desktop mode, and use the old reddit desktop interface. The more they modernized, the more entrenched I become.