AWS has an absolute tonne of great and not so great services but you can easily use the basic stuff to get quite simple and cost effective solutions. You can YOLO it on the console and not even worry about cloudformation if you want, and if you have no customers it will likely be free tier to boot.
Even then, your founders might have made a bad business decision – which isn't unusual, and companies can often make bad business decisions, such as prioritising investment in scalability when it's not a required feature.
They can equally make good business decisions – such as rolling out a relatively standard technology like Kubernetes to gain the workflow and availability features, even though scalability is not required.
I agree that it is important to remember that sometimes "old-fashioned" approaches can be totally suitable for some use-cases, and they can be too often written off. But equally let's try not to assume that everyone who rolls out a particular modern technology stack is a gullible fool.