On a 4k screen at 150% DPI scaling on Windows, in FireFox, I can see 30 items without scrolling on the current layout for https://news.ycombinator.com/

On this proposed format, I can see ten.

I believe the existing page is definitely more dense than it needs to be, but I don't think migrating to so much whitespace that it's 30% of the information that it was is a good ratio. I think I'd be happy with anything over 20 readable headlines (without scrolling) on a new format.