I dislike the snap store as well, but what you describe is how packaging works on Debian as well. Anyone can make, maintain a package. And there are people there that maintain even more packages.

However, there is a difference when uploading it to the repos, you either have to be a Debian developer or find one to sponsor your package first. After a while of doing good work, you can also request becoming one yourself.

This additional burden makes it more difficult for malicious people to go through.

Personally I prefer this separation of software developer and package maintainer, because that makes it a bit more difficult for malicious devs to push packages directly or for them to not package them the optimal way for the distro.

In addition, phone manufacturers write bad code, that would need to go through many review iterations until the open source community is happy with their changes. Often their changes to the kernel break things for other hardware, for instance.

Review and writing good software takes time, and phone manufactorers don’t care about long term support, they want to sell you a new phone every year, or even more often. So they fork the kernel and hack together with lots of string and duct tape, a frankenstein kernel that just works on their hardware, but is broken for anything else.