“And if you tie yourself too much to their proprietary managed services or serverless offerings, you'll find it very difficult to escape, once the bills start going to the moon.”

We (very large company) have been migrating to AWS for a couple of years. Of course as part of the package Amazon provided some "experts" who "guided" us to what technology to use. The answer of course is all the AWS-specific ones. Most of our teams are so embedded into AWS-specific tech now, it would be a near rewrite to leave.