There is no such a thing as "Cloud Agnostic". Be it K8S on AWS or Azure or GCP, each one has its own quirks that will make K8S run better or worse or even terrible.
Abstraction of some things on orchestration level does not mean there is no and will be no cloud specific code injected there. Actually there is a ton of this cloud specific code in there and when something stops working the way you want it to -> the solution often times is to write even more vendor locking code.
Instead of looking for "Cloud Agnostic" solution, find a solution that fits your use case the best. Using managed services if researched correctly can give many adventages. But like with everything that requires A LOT of knowledge about them and your domain.
It's interesting that you say that. Are you talkign about the hosted offerings then? If I spin up my own k8s "on metal" in GCP, would there still be something GCP specific to it?..
Abstraction of some things on orchestration level does not mean there is no and will be no cloud specific code injected there. Actually there is a ton of this cloud specific code in there and when something stops working the way you want it to -> the solution often times is to write even more vendor locking code.
Instead of looking for "Cloud Agnostic" solution, find a solution that fits your use case the best. Using managed services if researched correctly can give many adventages. But like with everything that requires A LOT of knowledge about them and your domain.