I've kind of been using Debian 13 for awhile now (I'm on Unstable) and for me what's impressive is how polished a default Debian installation is these days. With Gnome, you literally can run it as is, no config needed. It just works.

That being said, I like Flatpak, so I installed it (was super easy and Flathub provides instructions), and I added a few Gnome Shell extensions (a Dock so my wife can find apps when she occasionally uses my laptop).

Debian gives you a feeling of ownership of your computer in a way the corporate distros don't, but is still pretty user friendly (unlike Arch).

I'd definitely install Debian Stable on a grandparents' computer.