I don't like flatpak or snap or any of them. System libraries exist for good reason, just because your computer is stupid fast and you have enough disk for the library of Congress a couple times over doesn't mean you should run a veritable copy of your whole operating system for each program. IMO it's lazy.
Sandboxing is a different thing though, if that's the purpose then it's doing it right.
This used an onLoad which isn't generally shown when you hover over a link in a browser. Most people, even devs, aren't going to jump on the console to check every link.
This isn't reddit, if that tool does the jobs effectively then great.