I use Debian, a lot, I happily run it on most of my servers. But I can completely understand that it's not great for the majority of users.
Stable is too stable for the average desktop user - often kernel is missing drivers for newer hardware models, or system libraries are too old for newer applications.
Testing works most of the time but is not stable enough. Most recent example; zfs, which is on 0.8.x, is completely broken in testing since the kernel upgrade to 5.10 in December. zfs has not (and prob will not) backported 5.10 compatibility to 0.8.x. Last I heard, the Debian maintainers were still not decided on if they are going to backport the 5.10 fix to their own fork of zfs 0.8.x, or if they're going to do the upgrade to zfs 2.0 already.
I had a couple of servers where I had stupidly enabled unattended-upgrades, which broke the filesystems and required recovery to make services start again. Annoying, but it was my mistake.
This kind of situation is completely expected and there's really no one at fault. But it is a good example of why vanilla Debian is not suitable for many users and use-cases. Mint does seem like a better Ubuntu, though.