Old still exists and gets heavy use a decade or so later exactly because regular reddit just doesn't work at all, even when you're logged in.
But even aside from opinions on their UX, they're aggressively experimenting with the login more... Even on the new UI I now semi-regularly see that I can read the initial post and one or two comments but as soon as I scroll past or try to expand a comment thread get a login prompt.
Old still exists and gets heavy use a decade or so later exactly because regular reddit just doesn't work at all, even when you're logged in.
But even aside from opinions on their UX, they're aggressively experimenting with the login more... Even on the new UI I now semi-regularly see that I can read the initial post and one or two comments but as soon as I scroll past or try to expand a comment thread get a login prompt.