Yeah, 3kliks isn’t that great. He doesn’t go that in-depth into certain things. For example, take this:
He goes over each subject too quickly. Doesn’t really explain why carving is bad (rectangles carving into rectangles isn’t the greatest way to show why it’s bad), and does a very quick and dirty job of explaining lighting.
If you’re some fag going to make some stupid TF2 orange map that looks ugly or another GMOD flatgrass/construct remake, then by all means, you should go with him. If, on the other hand, you’re looking for some actually serious mapping, don’t follow him.