I can actually remember what's installed on my system and how it's configured in a centralised place, even when I don't touch the configuration for a few months. It's actually better for "boring" systems that I don't touch the config of much - "why is that set up like that" is a question I can easily answer. Additionally, when I do want to play with new stuff, the various tools I'm given usually let me do that and go back to a clean slate if I'm not interested, without having to deal with heavyweight containers/VMs/etc.

Yep, switching between KDE and GNOME or xorg and Wayland is so much easier than on other distributions.

All your state is in one place - packages and configuration. On a typical system there is tons of hidden state - some little option you had to change but didn't document, some package you forgot you installed ... that's not that easy to reproduce or change-track without backing up the whole system. You could use Ansible to do it, but that's another can of overhead.

... at least that's my experience.