YouTube will be fine. It's big enough to implement enough tech that they can say they're doing what they can. In fact, they've probably had enough there for years.

Most content hosting startups are likely to be too small to need to implement any tech at all, so they're fine as well for now.

The problem is that now it's practically impossible for a startup to scale up. The route to an exit for any startup hosting content and serving the EU is effectively closed, which is going to make raising impossible, which in turn will make developing a solution impossible. This law cements YouTube as the market leader in a way that no one can really challenge. They've been handed a de facto monopoly. That's the problem.