I'd also suggest maybe adding the channel names (like the comment you posted here) to the app itself (although i think it's cool when it's unnamed and you get the old-school feeling of channels just being numbers).
Also, I'd love to have permalinks for the channels. Not for the individual videos themselves, but just a link that when sharing would bring somebody else to the same channel you're watching right now.
Another thing, although probably outside your control, is that I use a Firefox extension called "SoundFixer" that I use to force the youtube audio to mono (since a lot of channels are annoying to me using headphones, they pan the audio sources too hard left/right and it's super distracting), but it doesn't seem to work on this website, probably because of the way they're embedded. I don't know if this can be changed somehow, or have a mode to force mono audio (which would be also oldschool like old TVs with one speaker only!). It's probably too niche and hard to do though.
Also I don't seem to find any volume control except mute?
I suspect they never did this because they never wanted to make YouTube compete directly with cable TV. YouTube content is displayed in a drab click-click UI because they want users to not scroll deeper for the content that isn't sponsored (paid) all the way to the front pages.
The UI of YouTube hasn't changed in essence for ages, it's still page based with only a few (shrinking) trending lists.
I think the reason they do that is because it allows them to control what is prominently displayed across YouTube -- The same concept is used across most social apps, where there are few features for discovering new content. The pages display embarrassing low view metrics on non-sponsored accounts, even when they may have really great content, it's really a backwards way of controlling what trends, and subsequently what makes money for the platform and sponsored creators.
If real choice was allowed on most of these platforms, we'd see literally endless (new) options for interesting new content on a wider variety of topics from creators none of us know, but right now, with shrinking choice, we only see manufactured and heavily co-opted content creators like Mr. Beast, Kai Cenat, Joe Budden, Pewdie Pie, (etc)-- they are usually sanitized, coached, & trained personalities picked based on who sponsors them and based on what makes the most ad profit for the platform. Most of that content seems to be very rigged and fake to me, as they clearly have staff working out of view. I find most of that manufactured (Picked YouTube Influencer) content to be drab and over-scripted... I can't stand watching it on & off YouTube personally.
Interesting channel scroller... The way it plays content also seems to look far more lively than watching YouTube on the regular site for some reason. I'd love to easily see the option to customize what is displayed based on the YouTube channels I already follow, and links back to subscribe to channel content I like while watching. A feed for specifically music-related content (by genre maybe) would be highly useful.