I'm very sad to see it go of course but the writing was on the wall for a long time after the demise of all non-k8s container management systems.
This is the ultimate fate of tools like Nomad and services like ECS. k8s changed the game by providing a target API/platform that gained enough traction to force each of the large providers to support a managed implementation of it.
I miss my time working on Flynn, we were a very small team but we wrote some good software and I learnt a ton in the process.