This just feels like a myth to me at this point. Kubernetes isn’t hard, the clouds have made is so simple now that it’s in no way more difficult than ECS and is way more flexible
It's a complicated mess compared to something like a Nomad jobspec. That's one of the reasons we decided on Nomad while I was at Cloudflare.
It's been a while since I spun up a k8s instance on AWS, Azure, or the like, but when I did I was astounded at how many implementation decisions and toil I had to do myself. Hosted k8s should be plug-and-play unless you have a very specialized use-case.
Last I checked, managed k8s clusters weren't much more expensive than the compute they ran on.