Maybe I'm missing some of the nuances between KDE and Gnome, but I've enjoyed the out of box experience with KDE far more than Gnome. That said, perhaps I've simply timed my switchover to Plasma such that I missed its teething pains. I say this as someone who used pretty much exclusively Gnome over the years.

What would you say sets Gnome apart?

best hope for mainstream adoption

I feel for that the default Linux DE will need to have an UI closer to Windows, due to user familiarity with the traditional desktop metaphor. Maybe Cinnamon or even KDE are more suited in that respect. Neither need hours of configuring either. Personally, Cinnamon with Wayland support would be perfect for me (and I suspect a whole lot of Windows migrants as well).

Gnome is nice of course in it's own minimalist way for many,but the workflow is very different from other OSes and I think many find it too minimalist requiring extensions to improve usability therefore. However, there isn't a stable mechanism for extensions causing breakages between versions, which can be very irritating. I don't know if that's now changed now though, because I have been reading about a major change in the extension mechanism in Gnome 45.

I think several DEs could see mainstream adoption.

If the team that works on Cinnamon got a little bit more manpower and were able to implement larger changes such as adopting Wayland, I think they'd have a chance. Wouldn't hurt to make the default theme a bit nicer too. I think the main thorn in Cinnamon's side is the development pace and the fact that it would probably be viewed by the average person on the street as a weird Windows clone.

Plasma's largest obstacle to mainstream adoption is bugs and instability, but in fairness it has improved a lot over the past couple of years. Seriously, compare 5.27 to any Plasma 4 release or any Plasma 5 release before like 5.16 - it's night and day. Kwin still crashes and takes all your programs down with it, though. That's a showstopper, but will be fixed in Plasma 6.

Speaking of Plasma 6, the fact they keep pushing it back probably means they want it stable from the beginning. KDE are doing a good job putting the "KDE is buggy" statement to bed.

I guess I agree that Gnome as it stands is the most appropriate for widespread adoption. It's extremely polished and beautiful, it has comparatively decent accessibility features, it's extremely stable despite being a frequently updating distro, it has amazing gesture support (better than MacOS even, imo), it's decent in terms of touch support, the GTK4/Libadwaita app ecosystem is healthy, etc. but it's not completely without issues.

Unfortunately this is all academic though until big laptop OEMs start actively pushing for Linux on their devices.