This is a pragmatic choice. You are wise to focus on getting the product right before all else.

As for being tied to a cloud vendor, I have literally never seen this matter. It's like worrying about being tied to a specific programming language. You have to make decisions.

I find it funny that many companies who not long ago were hosted out of a single datacenter, today see the need to be multi-cloud, multi-region, and running k8s. There are exceptions but it's far from the rule. Build a product FIRST.