Startup: use <aws|azure|gcp> because it's quick to get started. It's easy to scale it up 100X in 5 minutes for when you make it big. And it provides a long list of easy to use services that are overpriced per use, but which free you to focus on your business rather than complex DevOps.
Then once you scale to the point that you're comparing your salaries and your ops cost, you find smaller services to handle the expensive part of your business. Ones that do exactly what you need, not much else, and charge accordingly. Maybe they're self-operated, or maybe they're other companies with a narrow focus.
Then you write a blog post about how everyone is crazy to use <cloud> since it's so expensive, and you don't know why you ever thought they were a good idea.