What's the issue? I installed mint because I know fuckall about Linux, and tbh it's a dice toss if I have used the Flatpak option not knowing what the actual difference between them are
Honestly, you don't have to worry about what others say, you should use what works best for you. Personally I find them to be nice and comfortable to use, myself 😅
I'll add upon what others have said here, for me the main downside is the size they take on disk since they don't really share dependencies (they do but not as efficiently as native or nix packages) so they take a lot of room and take a while to update. Otherwise they're amazing IMO and you should use them! :)
Thing is, if your flatpak software needs something not in its container, it gets a little complicated, because first you have to realise what exactly the problem is and secondly you have to use something like flatseal to give it access to wathever it needs to work (no real help there)
So this was what took me back to pacman (or better said yay)