This is really a statement.
Last year I started studying OpenShift Administration I (DO280) but didn't pass the exam.
I felt good about my 'infrastructure' experience, just not my skills assembling applications and working with Kubernetes resources.
I took DO290 and felt like it does a great job specifically with working with the json files that are used to create various resources and provides a concise strategy for how to assemble a template file from the pieces.
For folks trying to build knowledge with OpenShift, I'd recommend this course.
Glad to hear you liked DO290!
I dare say that if you did, you will probably find DO288 an even better course for end-users. It really focuses very much on the things that matter to developers and SDLC engineers and tries to be goal-oriented and educational at the same time.
It is also very much modernised in the sense that it uses newer syntax approaches, introduces some cool tricks that we never talked about before, and almost completely eliminates any need for JSON/YAML editing as a consequence.
In my teaching, I always show and explain the JSON and YAML, because it makes so much sense to know what the various attributes mean, but I also point out that there should be very, very few use cases where you actually have to edit resource definitions directly.
You'll also be happy to hear that with the new Operator Console, admins will soon be able to avoid direct resource editing as well!