Old reddit is more like BBS or old school message boards. People who grew up on this are a dying breed... probably also worth less to advertisers as we use adblock.
The things which drive me nuts about the redesign are mostly things that drive me nuts because I comment far more than I post, and participate in a lot of discussion-heavy subs. Navigating comment trees is more difficult, lots more is hidden by default. Far fewer topics fit on a screen with the card-style layout that has huge previews. The old layout is information-dense, readable with minimal clicking to expand things, and fast.
But those are exactly the kind of changes that someone just browsing would be indifferent to, or even appreciate. The images/videos they're scrolling through are now big, front, and center. Many probably don't ever venture into the comments to begin with, of if they do, they're just seeing if the top comment is a good joke or not.
Wildly different use cases.
It really depends on the type of consumer. I don't post to reddit anymore, but I'm not looking to consume memes and videos. When I go there I'm almost always looking to consume a comment thread about something (say some weird feature of some motherboard), and the new UI is atrocious for that. I either switch to old or I don't bother with it.
What reddit should have done is to ship the RES UI with the old reddit interface.
I definitely don’t think people preferring this layout are a dying breed, but I do agree that it’s easier for them to monetize the new layout.