digg died fifteen years ago. clearly a lot has changed, and the mistakes that killed digg have not been made.
and i think reddit is beyond the point at which a digg-style fuckup could kill them. at worst you might see cadres of ideological users depart for something like lemmy, which is already happening to an extent, but there is a lot of space to flee internally, so most users don't feel the pressure. and diffusion to federated media is in the future for every mass audience. reddit has such a huge and active userbase it will dominate for the foreseeable future.
The new HTML layout and the obnoxious mobile website are worse than what killed Digg, IMO.
The difference is that when Digg made their mistakes, Reddit was there for the taking.
Nowadays, there's no alternative to Reddit. All the new sites appear to be focused on hateful communities banned from Reddit, and that will never attract the mainstream.
Digg closed before it was defeated really. I can't remember if it was the v3 or v4 that caused the migration but they didn't even try to roll back... or just stick with their new plan. They just gave up it seems.