I feel like OP would've been much better off if they just reworked their cluster into something sensible instead of abandoning K8s completely.
I've worked on both ECS and K8s, and K8s is much better. All of the problems they listed were poor design decisions, not k8s limitations.
- 47 Clusters: This is insane. They ack it in the post, but they could've reworked this.
- Multi-cloud: It's now not possible with ECS, but they could've limited complexity with just single-cloud k8s.
47 clusters is major "we didn't know what we were doing"
At my last gig we were in the process of sunsetting 200+ clusters. We allowed app teams to request and provision their own cluster. That 3 year experiment ended with a migration down to 24ish clusters (~2 clusters per datacenter)
> As the number of microservices grew, each service often got its own dedicated cluster