I consider the "best-in-breed" tools with this shape to break into the following categories:
"Infra Abstractions": DuploCloud, Massdriver, Stacktape "PaaS in your own cloud": Nullstone, Zeet, Quovery, Porter, Architect.io, FlightControl "SDLC Platform for Teams": Coherence (withcoherence.com) - the key difference here is in how CI/CD (incl integration tests) are handled, how development environments are configured alongside other environments, and how production is segregated from other environments.
This a somehow both a crowded space and an emerging one. But we believe that even with the diversity of choice that there are clear reasons that most teams will by (vs. build) their internal dev platform in the future: namely the cost to buy vs. to build/maintain, and the productivity from better tools.
There are nice perks on this approach but the complexity (for us) is non-negligible.
However, Kubernetes is more a primitive for infrastructure rather than a tool to build automation workflows for software teams. Our focus is to complement teams that may or may not choose Kubernetes.
Kubernetes is an incredibly useful tool, but it needs at least one layer of abstraction (possibly multiple) on top of it to make it useful for the typical company that isn't doing anything out of the ordinary.