Because the browser is so much a part of my use of the system -- not just to websites but also cloud apps and even localhost stuff -- that I think it's important to have a default browser that's a system package (.deb), closer to the iron and quicker to start. There are a number of places with instructions on how to:
1) add the firefox ubuntu PPA repository.
2) ensure that the .deb Firefox has priority over the snap one
3) (optional) delete the snap Firefox and instruct snapd to not try to reinstall
Other apps I have less of a problem with, though I do prefer flatpaks over snaps partially beyond the size issue that you raise and the systemd dependency that is important to Steve. Primary to me is the massive single-point-of-failure in play given Canonical having tight control over the repository.
Been there. Tried Mint KDE and then Neon and Tuxedo and even Bazzite, now back to Kubuntu. It's not just fear of the unknown, it's also that the based-on-Ubuntu distros will by definition always be slower to deploy. Even if they fix things Ubuntu breaks they are always in reactive mode. Plus developers that have limited resources and can only officially support a few distros will always have Ubuntu in their lists.