I use it on mobile. Still better than the new site. Chrome has bugs with the "text scaling" feature but if you turn it off then old.reddit.com works fine.
In posts with embedded pictures, I have to remove the "old." in the URL in order to be able to see the pictures, switching to desktop mode doesn't solve the problem.
Ed: to be clear, I use it logged in. I don't know how dark-patterny it is when logged out.