As far as I understand, when you land on an AMP page, you get the same (cached) page that everyone else gets. Which is basically a shortened version of what you would see if you were not logged in. So while it may not be AMP's fault, AMP enables/encourages the behavior.

If the AMP page is showing everyone the same thing, then of course I won't see Reddit with my user settings (old mobileweb, do not ask me about the app, etc), and of course trying to interact with the page will redirect me somewhere else.

If I could opt out of AMP to avoid this issue, I would. If there were no AMP, I could reasonably expect to arrive at Reddit as I normally see and use it.