We do. Our stack is a fairly standard Java app on an oracle dB. Seems to work well enough. We couldn't get the app to work with azure and aws is a no go (we have retail clients)
and to clarify on the above reply, it's widely suspected that Amazon snoop at data hosted on AWS, so they can make/sell competing products that are selling well based on what they learn from snooping.
So basically any business that makes or sells anything that Amazon may possibly make or sell in the future doesn't want to touch AWS.
Do you imagine the fallout if it came out ( and how would in not, thousands of people would have passed through, one disgruntled employee is enough) ? AWS would lose most customers within a few years, Amazon.com as well ( disgusted buyers and sellers), there'd be lawsuit everywhere. I really don't think anyone in Amazon is stupid enough to risk a trillion dollar business for some potential competitive advantage on whatever sold on Amazon.com
Amazon has regularly launched products with their "Amazon Basics" brand, copying well-selling 3rd-party products sold on Amazon.com, always a few bucks cheaper. [1]
What makes you think it would be different with AWS?
I doubt that actually looking into EC2 instances (which AWS would never do, "pinkie promise") would even be necessary. Metadata about the company's deployed infrastructure would totally suffice to derive enough business insights to launch a "knockoff product", as you call it.