A simple approach would be to add a short "New" section at the bottom of the frontpage, which shows about 5 semi-randomly chosen submissions from the last few h

A simple approach would be to add a short "New" section at the bottom of the frontpage, which shows about 5 semi-randomly chosen submissions from the last few hours that haven't seen much engagement yet. That would encourage more curation without much effort, but also without too much distraction for users only interested in the top. Add a toggle to hide the section persistently and everyone should be happy.