>If the new version of Anki needs a new version of a dependency, just install the new version alongside the old one.

Yes, and do that with every other package as well.

Are you even considering the implications of what you're saying? The next-to-latest version of Anki is for example in the repos of the most popular distribution. The latest version of Anki is not in the repos, and its dependencies break something in that distro.

You're free to install Anki's latest version, but there are reasons why stable distributions will not just jump on the latest version of a fairly unknown package.