You can rewrite code deployment script for any provider in few days worth of work, but switching between other tech stack will be near impossible.
I've directly experienced the counter example to this at a major SaaS company. Beyond methods you'd use for < 20 machines this just isn't true. Your orchestration of machine lifecycles will be tied up into the particular cloud no matter what kinds of abstractions you try to put in. Unless you start running on multiple clouds or you write to k8s instead of the cloud APIs, you will be locked in.
I agree, and the advent of k8s adoption is one less thing that locks you into a provider.