I'm not sure what exact device you're using, but on iPhone 12 Mini, old.reddit.com is borderline unusable, very different experience compared to if you could access r/all like before via the actually usable web+mobile version, a comparison: https://imgur.com/a/AVGjjCN
Anyways, the end result has been I don't use reddit at all on the phone, so kind of ended up being good for me anyways.
“Borderline unusable” is such a hyperbolic way to describe a fully functional design that doesn’t happen to be responsive. Hacker News must be borderline unusable for you as well then, no?
It's perfectly fine and usable for me. More so than the app or the 'new' Reddit design. I exclusively use the old design.
I'm using an iphone 13, although I prefer to turn sideways and browse in landscape mode. What you consider borderline unusable is just how I prefer to browse reddit.