Package managers are the only sane way to install software. Even Windows + Mac OS somewhat came to realize this (even though their implementations are terrible compared to what we have in Linux land).
It's shocking that people disagree with this. Do you really want to go back to the days where you had to download installers from the internet or copy-paste random 'curl | sudo sh' lines?
Running software shouldn't even have the file permissions to change anything about its own installation.
Note that you can still do things wrong even if you're doing "package management".
This morning I updated Firefox through apt, and suddenly the "running" Firefox windows weren't attached to the dock icon, and clicking on the dock icon launched the new FF installation.
Also, Ubuntu's "snap" approach to installing apps is a nightmare that causes no end of problems - unless they ended after I gave up on it. Multiple installs overlapping each other, and I once even had the Firefox snap using a downloads folder in the Skype snap's local data.
Honestly, even with package managers handling all the nitty gritty applications should still be written in such a way that they can quickly sync their state to disk and reload it so that after an app update the app can quickly re-launch with the updated version rather than risking a mix of old and new.
It's shocking that people disagree with this. Do you really want to go back to the days where you had to download installers from the internet or copy-paste random 'curl | sudo sh' lines?
Running software shouldn't even have the file permissions to change anything about its own installation.