The hacker news crowd is overwhelmingly in support of old.reddit. I mean look at the UI of this place. Obviously this crowd appreciates substance more than Web 3.0 ad trackers and GIF chat
If everyone loved it, there'd be no Hacker News mobile apps.
The only things I would change is make the Reply link open a text box in-line rather than needing a new tab, and add an icon next to my username/karma in the top right whenever there's a new reply to one of my comments.
Any other "modernization" is probably a step BACKWARDS in UX. I really like the simple design of HN.
If it were your site, suited to the current year, I wouldn't come back here.