I agree with you about 90% of the way, in the fact that its starting to get ridiculous with the amount of people who just come on in order to advertise their channels.
However, the simple fact is that it is the creative corner after all. its where your meant to post drawing, stories ideas, and even videos in order to get creative feedback in return. So unfortunately, its kind of one of those things where people shouldn't do it, but can because that's what the section is there for
I think the best way to solve the problem would be:
A: make a new section just for youtuber stuff. I know this seems kind of bad at firs, but it would also allow people to talk to one another about things based around youtubing and whatnot rather then just "Check out my channel!" (Btw, I know this will just end up as people posting about checking out their channels, but at least it separates that side of things from the other side which actually requires creative criticism. E.G: my sections on creating a multiverse got buried under that mound of stuff and I don't ever get feedback on it ;-
B: As you said, just delete the ones that are literally just "Check out my channel" And add a notice to the section stating to people not to publish anything that's just "Check out my channel"