Because saying "learn songwriting" is as useful as "learn painting" when you want to make stuff like van Gogh.
I mean, it's what you have to do, but it conveys so little information by itself that it's ultimately useless.
He says he doesn't need gear recommendations, and wants guidance. Those are the three primary things to learn in order to make music like he is interested in. Learning compression use or other engineering stuff is not a primary concern. There is no step by step method to do anything well and with your own twist on things, but surely at least narrowing down the fields (even very basically) is better than lecturing him.
If he wants to be Van Gough, you're not gonna recommend he learn Photoshop, right? You're not gonna tell him to work on silk screening skills, are you? It may seem quite obvious to those of us with deeper knowledge how these things are done but I can remember when it was not.
I came to the hard truth that there is not a simple answer for these productions and that you must lock yourself in a studio and figure shit out yourself.
I think you have answered your own question.
Youtube is your friend. There're videos on anything and everything on there. I certainly learned a lot there.
As for the track you posted, it's not that complex. A beat, a bassine and someone rapping, the "clever" bit is that it sounds like someone is messing around with a vocal processor while they are rapping.
If you want to emulate the people you listed (it's a good list), learn how to play. It's a slow process but ultimately rewarding. You can read up and experiment with all the techniques as you get better.