So you write an abstraction around the provider, and when you switch provider, you still need to implement a new implementation of that abstraction for the new provider. So in this regard, docker gave absolutely 0 benefit.

In regards to setting up a new server for a new provider, or docker, you have some boiler plate:

-> create script to attach docker to provider

New provider...

-> create new script to attach docker to provider

----

-> create script to provision server on provider

-> run generic script to configure it how I want

New provider

-> create new script to provision server on provider

-> run generic script to configure it how I want

In this regard, moving from 1 provider to another, is identical.