I think at scale, K8s is a good choice. I run a Discord server with like, 3,400 members now, and some of them are working at mental scale. They've claimed the same as you: K8s at scale is the only way.

I would very likely agree in all cases.

However, they only represent 4-5 users out of all 3,400. And that's the issue - only a small fraction of the industry operates at that scale :-)