In my experience, the Debian installer is just confusing. Once you're past that, the userbase is smaller than Ubuntu's. Their repos are different too, meaning software packaged for Ubuntu isn't guaranteed to work on Debian. Ubuntu itself is pretty terrible for its own reasons, so when asked for a desktop Linux distribution "close to Ubuntu" I'd put Mint first. (For general recommendation, I'd probably say Fedora now.)
Debian 13 is still relatively new, so the problems of it being out of date aren't showing yet. Debian 12 just before 13 released had tons of these issues, like glibc being too old for some binary programs, or the kernel not being new enough for some "gaming" features.
For reference, I am on Arch Linux. I feel I have a good understanding of how to manually install Linux. The Debian installer confused me in many ways, the main one being that "language and region" are closely tied, and selecting en_US "language" forces you to choose an American timezone later in the installer. In general it was a slow install process too. This is something other "user friendly" distros handle much better. A default live environment, a quick installation, and options being there, but having the defaults automatically correct (like timezone).
Like (almost) every other distro, Debian has its own benefits and downsides. These make it a good fit on desktop for slightly more experienced users, or users familiar with apt. This means it isn't in the list of distros I'd generally recommend to people when they're not familiar with Linux.
It's the task of your CPU scheduler to ensure your system doensn't freeze, even over 100% CPU usage. If it's completely unresponsive, it's more likely you're running out of memory instead.