The real benefit of the cloud is their SaaS offerings. If you go cloud agnostic you create more on going maintenance overhead (since you now have to manage services), higher hosting costs and you still have to rewrite most of your IaC when switching clouds anyway. Contrary to common belief, IaC platforms like Terraform doesn't mean the same code works across different clouds. It just means the same language can be used to provision services. However how you define services in that language will differ from one cloud to another even if the types of services are the same.

So unless you're going multi-cloud from day one, it's much better to write your services to be specific to the cloud you're using and benefit from them rather than boycotting them because of a theoretical decision of multi-cloud that you might never actually make. Most companies that talk about going multi-cloud never actually do because the benefits of being multi-cloud are actually pretty small for most domains. Being multi-cloud is one of those things that sounds more important than it actually is.