[mcphage]

The biggest difference (as I understand it), is that in classical roguelikes, nothing persisted from run to run. In modern ones, you build your character up over a sequence of runs, so that in later games you're more powerful and can go further. But in classic roguelikes, every run is like the first. So a player's knowledge is the only thing that does keep—they learn the game better, learn the systems better, and progress further because of that. Not because of anything they unlocked in-game over a series of runs.