Not snarky at all, you are more correct than you may realize. The upgrade is a challenge because we move from RHEL 7 to Red Hat CoreOS 8 as the host OS, as well move all the OpenShift code to operators instead of in the binary. OpenShift itself can now also manage the nodes (thanks to RHCOS), as well as fully self-upgrade. For container runtime we move from Docker to CRI-O (for a number of reasons, high on the list is security). It's a massive overhaul which is really more akin to a brand new product than a major version. I generally can't stand major overhauls because most of the time they don't give you much new and often bring regressions. However, this really was a tremendous improvement, the fruits of which are not even fully realized.

Because of that major change, the cluster upgrade path is a little more involved than usual. It's a complete reinstall of the OS and rebuild of the cluster. There are tools to help tho, and as the path is tread things will get easier and better supported. If you go through the same wave as me, you'll be annoyed at first but then once it is done and you have a 4.x cluster you'll be really happy with it (especially when you can manage everything as an operator).

Luckily from an app perspective very little will change since Kubernetes is the API. A sibling comment linked to some helpful documentation. I can't be specific right now but I can tell you that your need is known, and some very smart people are working on it. If you want to email me (check my HN bio page) or jump in the Keybase group called "openshift_okd," I'm happy to chat more about it (not in an official Red Hat support capacity, just as friend to friend :-) ). I haven't done a migration myself yet but I know people who have, and I plan to get into it personally soon as well.