Do you understand the concept of competition under capitalism where the govt isn't forcing a single entity to the top?
The point is that advertisers essentially decide what's permissible and what isn't. An alternative to youtube backed by advertisement from major brands would have to abide by the exact same model.
On a more pragmatic note, the reason people use YouTube is because everything is there. Competitors like DailyMotion and Vimeo exist and do compete, their content libraries are pretty pathetic though, and the advertising situation is no better than YouTube.