I don’t understand what problem they are meant to solve. If you have a FOSS piece of software, you can install it via the package manager. Or the store, which is just a frontend for the package manager. I see that they are distribution-independent, but the distro maintainers likely already know what’s compatible and what your system needs to install the software. You enjoy that benefit only through the package manager.
If your distro ships broken software because of dependency problems, you don’t need a tool like Flatpak, you need a new distro.
Frankly I loved my Commodore 64. My Linux box is better in every measurable way but there was something to simplicity and a time where just making a sound and drawing on the screen with a computer you could afford was quite a thing.
Same with Python. Started using it about 1998. It was simple enough that I learned the language in a day. Now there is so much more. Then add packages for everything these days… lot of the work is understanding packages, venvs, how to deploy, not just opening idle or pywin and writing stuff. Sure Spyder or one of the other IDEs can do static checking, have doc at your fingertips, integrate a debugger, and have a graphical shell where you can do all sorts of stuff. Changes the feel of programming though.
Hehe, that’s called nostalgia. I can feel that, too. 😊 Things used to be simpler but that had some appeal to it. And a different vibe. And you had to work hard. That made your achievements more rewarding than spending your time fighting with complex buildchains.