I am definitely not a fan of Zoom either and had my own issues with the Linux client, but if the problems you describe are unique to the Flatpak and not in the official Linux distribution, you can't blame Zoom for that.
It's not like a flatpak packager says "ok let's implement the GUI framework from scratch".
So, yes, I can blame Zoom for sure!
If by some chance flatpak packagers need to re-implement all the GUI calls manually, then it is a miserable failure as a packaging format and needs to be terminated immediately. But we know this is not so, right? Nobody would be that stupid as to require hand-coding the GUI all over again, right?
The reason why I commented in the first place is because you explicitly mentioned the Flatpak of the Zoom client which stood out to me.
It is my understanding that Flatpak sandboxes apps [1], which could cause various issues if the app is not expecting to be run inside one or of the permissions are misconfigured.
But it certainly doesn't have to. Of course the app itself can be buggy. My point is that an official release should be checked before reporting bugs.
[1] https://docs.flatpak.org/en/latest/sandbox-permissions.html