True; as said, this is Debian Testing. By "major issue", I mean Grub occasionally gets borked and I have to chroot in and fix it, or the time_t_64 transition.
I found the compromise between stability and newer packages acceptable for my desktop machine, which I am usually only on when I would actually have the time to debug these things. However, these days, I'm busy, thus may switch to stable in the next few months.
Honestly, no. I just use direct apt commands on my Debian installs for native stuff, assuming I even use the shell for that; sometimes, if it's not a complex update that's going to hold back 1.0*10^6^ packages, I just use Synaptic or Package Updater, frankly, as one of those is what I have my XFCE Package Update Indicator set to use on any machine I use frequently and it's convenient sometimes.
As for Flatpaks, I just run the flatpak update command whenever I feel bored. I wish Warehouse GUI supported updating, just because I find it really weird that's excluded from an otherwise pretty slick application that gets rid of me having to muck through the Flathub.
I don't write Rust code at the moment, and as for Python, I'm either using the Debian version of Python packages or scattered venvs that follow a de facto standard for Python developers: "What's an update?"