I’m less worried about Videos and Terminal: those are very “low chrome” apps, so even if they don’t look up to date it isn’t going to be tragic; I care more about the video or the console than I care about the menus or buttons. Totem, on top of the mere GTK4 port, has also to drop a bunch of legacy components at the same time, which increases the effort.
Evince has been low on maintenance for a while, so I guess we should try and help Germán out, and possibly find new co-maintainers. I’d be happy to help with the review of the GTK4 port, though I can’t guarantee I’m going to be able to pick up maintenance as well.