It's all very well knowing what you should do in theory, but that's pretty useless if you don't know how.
I've also never heard it be called "enumeration theory" before.
If you want more up to date material in this kind of field, something like the Red Team Field Manual (https://www.amazon.co.uk/Rtfm-Red-Team-Field-Manual/dp/14942...) or "Advanced penetration testing" https://www.amazon.co.uk/gp/product/B06XCKTKK8/ref=oh_aui_d_... could be worth looking at.
And the floating modal on the center of the screen further proves my point.
But I fear finding a lack of practical hands on stuff (I would want to bring up an aws instance that is vulnerable in ways x y and z and have to find them. Or something)
Does such a course exist
OSCP is a useful entry point in terms of what it teaches.
But there are also loads of free resources which can provide some hands on examples
https://pentesterlab.com/ is one example which has some good free examples as well as paid for additional content.