The monopoly issue won't be resolved so long as there is artificial exclusivity over the content, i.e. copyright. That's the most critical monopoly of all. Different streaming services can't compete on how good they are at streaming because their content isn't interchangeable; you can't just swap one show for another even when they're similar in style and production quality.
The absolute minimum requirement to resolve this would be obligatory "reasonable and non-discriminatory" mechanical licenses allowing any streaming service to stream any content on equal terms regardless of source.
Unreal is "source available", not Open Source. There's a big difference. With any Open Source project you can legally fork the project, distribute your custom version of the code, create a community around your variant... "source available" has none of that. The Unreal EULA is more permissive than most game engine licenses (with the obvious exception of Godot) but it still comes with plenty of restrictions. For example:
Which pretty clearly does not satisfy the Open Source Definition.