A big chunk of YouTube's dominance comes from Google's other lines of business including online search and online ads. See the other post today from a former competitor[0] for an example.

The reasoning is that stripping YouTube of Alphabet's deep pockets from advertising would give competitors a chance to monetize as well as YouTube, without fearing that Google will choke off their air supply to preserve YouTube's dominance.

It might not be enough, but it would be a start.

[0] https://news.ycombinator.com/item?id=20472351