SHOULD desktop apps be like this? :D
For programmers and experts no.
But if it was toggle-able, I would toggle "sandbox everything, don't let anything not secure run, only allow trusted apps" in a heartbeat for work machines, my parents, and so on...
Maybe. I'd argue "extremely".
It does suck, for instance, that Discord as a Flatpak can only access a fixed subset of $HOME directories. But it can't scan your machine's processes like ordinary Discord can (to report the game you're playing), which is a privacy gain. The security (and portability) advantages of sandboxing/containerizing apps may outweigh the hassle of the workarounds/memory inefficiency.
Meanwhile, with unfettered access, you have things like: https://www.thegamer.com/civilization-6-steam-eula-change-sp...
>"We may combine the information with your personal information and across other computers or devices that you may use"
They also mentioned "photo", which there's no obvious way to collect. I remember someone joking, "What, do they go through your directories, looking for a picture of you?!"
So maybe, instead of trying to somehow make it safe to run untrusted software on our machines, we should focus on making sure all the code that runs on our machines is trusted - not in the sense of "proved correct", but in the sense of "written without malicious intent". If you regard Discord scanning your processes as an unacceptable invasion of privacy, and it bothers you that there's no way to turn that off, perhaps avoiding Discord is a better solution than trying to sandbox it.
Using a separate computer for each counterparty would be more secure, but again not very convenient.