They already killed the lightweight mobile version at i.reddit.com last month or so. I wouldn't be surprised if old.reddit.com is on the chopping block within the next few years.
I think the new design at https://sh.reddit.com/ (for desktop PC) is aimed at this. It's supposed to be better performant than the current design and dealing with criticized decisions like the heavy layered design, but I think another way to view it is that it's supposed to finally kill old.reddit.com once released, probably in a year or so.
That's unfortunate. This design still lacks information density. I use old.reddit because I don't need my front page covered in preloaded photos, videos, etc., and I like to be able to see things in a dense format, no scrolling required.