The dirty secret of virtually every k8s setup--every cloud setup--is that the cloud providers' stuff is simply too good, while at the same time being just different enough from one another, that the impedance mismatch will kill you when you attempt to go to multi-cloud unless you reinvent every wheel (which you will almost certainly do poorly) or use a minimal feature set of anything you choose to bring in (which reduces the value of bringing those things in in the first place).

"Vendor lock-in" is guaranteed in any environment to such a degree that every single attempt at a multi-cloud setup that I've ever seen or consulted on has proven to be more expensive for no meaningful benefit.

It is a sucker's bet unless you are already at eye-popping scale, and if you're at eye-popping scale you probably have other legacy concerns in place already, too.

This.

The whole point of k8s, the reason Google wrote it to begin with, was to commoditize the management space and make vendor lock-in difficult to justify. It's the classic market underdog move, but executed brilliantly.

Going with a cloud provider's proprietary management solution gives you generally a worse overall experience than k8s (or at least no better), which means AWS and Azure are obliged to focus on improving their hosted k8s offering or risk losing market share.

Plus, you can't "embrace and extend" k8s into something proprietary without destroying a lot of it's core usability. So it becomes nearly impossible to create a vendor lock-in strategy that customers will accept.