Now I have been using Gnome 42.3.1 a couple of days and I must say;, you don't miss much by using Gnome 3 on Zorin other than the gnome team are phasing out custom theming and removed some features. There are probably some under the hood enhancements too.
The grass is not always greener.
I've had quite a similar experience after spending the last four months or so bouncing around different distros. I was happy on Zorin, but then ended up hopping onto Fedora 36 and then Ubuntu 22.04. Both were fine, but then I wanted to give Elementary OS a try again, which I did, and ultimately I ended up back on Zorin 16 where I started.
One thing I found interesting is just how much lighter Zorin feels to use, even with its older GNOME version. On Fedora and Ubuntu, using GNOME 42, window animations were hitching and skipping where on Zorin, everything is smooth as silk. If you keep your applications coming through snaps or flatpaks, it's a very stable experience with all the latest applications and it still looks and feels fresh.
Glad you are happy with Zorin 16. I will still not use flatpak or snapd where I can avoid it. Once you are down either of those rabbit holes you lose control over your system.