There is no such thing as trivially setting up a secure, fully automated cloud stack, much less anything like a streamlined cloud agnostic toolset.
Deprecated services are not the discussion here. We're talking tactical availability, not strategic tools etc.
Rogue employees with access? You mean at the cloud provider or at your company? Still doesn't make sense. Cloud IAM is very difficult in large organizations, and each cloud does things differently.
I worked at fortune 100 finance on cloud security. Some things were quite dysfunctional, but the struggles and technical challenges are real and complex at a large organization. Perhaps you're working on a 50 employee greenfield startup. I'll hesitate to call you a clown as you did me, because that would be rude and dismissive of your experience (if any) in the field.
K8s is one of a hundred technologies to learn and use, and just because each cloud is supported by terraform, you can't swap a GCP terraform writer over to Azure in a day.
And no bank is without their uncloudable components.
Example: Payment/Administrative issues, rogue employee with access, deprecated service, inter-region routing issues, root certificate compromises... the list goes on and it is certainly not limited to single AZ.
A very good example, is that regardless of which of the 85 AZs you are in at aws, you are affected by this issue right now.
Multi-cloud with the right tooling is trivial. Investing in learning cloud-proprietary stacks is a waste of your investment. You're a clown if you think you need 25 people internally per cloud is required to "do it right".