That ignores any other libraries you use which may not make the same choice as you.
It doesn't. You stick to the version of those libraries at work with that version of the compiler- like every other language.
The difference is that most other language are backwards compatible to a fault (it's hard to have the stability cake and eat improvements)
That's fine in a vacuum, but I feel like you'd very quickly run into the need for a security update, or some external API that changes, etc. You can't ignore all externalities, usually.
Then you risk missing the deprecation warnings and head straight into errors.