The best part of the internal Amazon stack is the relative consistency across the company. Not that every team is using the same thing, but it's a reasonable assumption that whatever particular combination of things you're using, someone else probably is too. It makes it really easy to work around the sharp corners present in any stack. Additionally, basically everything is internal-only or AWS, so the people who developed the tech stack are all just an internal search away.

That said, I've done just fine without that benefit since moving on.