K8s is a "middle 80%" scale solution. Its not made to run Google (though Google uses it a ton internally). Its also not made for your average four person startup (though, if you've got that experience internally, its not a bad choice; its not Heroku, but its better than a lot of deployment options out there).
All I'd say is: I've worked in a "scale-up" B2B org under $1M in ARR. We were pretty monolithic; just a backend NodeJS app, and a frontend SSR React app, basic. Five engineers by the time I left. We used K8s (EKS+Fargate). Maybe 50 pods total, across two environments. It was fantastic. We never had to say No to any weird customer, product, or engineering decision which would be difficult in either more managed, or more legacy, systems. Customer wants a custom domain and'll pay $50k for it? Like five lines of YAML and update Route 53, done. Datadog sidecar container so we can ingest some APM traces? Ten lines of YAML copy-pasted from their docs, done. Update the cluster? Click one button in the AWS UI. Every developer wants their own staging environment? Ok, bit more work, but: create some namespaces, retool the CI a bit, we can deploy separate databases in there as well its only staging, actually pretty straightforward.
Half the stuff we did with k8s would have taken three times as long with more native AWS solutions, and some of it probably would have been impossible on something like Heroku. K8s strikes a balance. Its not the simplest thing in the world. I wouldn't grab it on day 1 of a startup's engineering journey. But I wouldn't knock a startup who does.
