Not sure why you get the downvotes, all I can imagine is that there are a lot of people here who learned on K8s and have never tried anything different, or had to manage infrastructure at scale (In my experience scale being 30k+ bare metal machines)

99.9% of the time I see a k8s implementation it's a shop pushing a ridiculously low amount of traffic and then needing to scale their application across decades-old hardware provided by a cloud provider. It's so bad that a single, modern 4U server, like I used to manage working at at a large company, could have replaced their entire infrastructure. The k8s users wind up with thousands of lines of YAML to solve a problem that could have been solved with better design decisions. The abstractions upon abstractions also prevent developers from truly understanding what is going on in the real world, for example your cloud provider's hypervisor doesn't align with your para-virtualization hypervisor so you end up with all sorts of issues with affinity and noisy neighbors on the same hardware that you can't even see, or your racks aren't splayed right so failures wipe out disproportionate amount of instances, that K8s then takes ages to rebalance things.

As far as the statement "there's no reason it should be as simple as Heroku", I agree completely. I imagine in a few years something like AWS Firecracker+ a simpler control plane will end up superseding k8s, and k8s will end up in the graveyard of dying virtualization orchestrators like OpenStack and CloudStack.