Unity has been rent seeking for awhile. In my mind, a big issue is the unity asset store, which apparently is where they actually make most of their money. Unity collects a 30% cut of all sales and imposes pretty restrictive licensing terms. This is annoying, but not a huge deal for things like art assets, but it creates a huge perverse incentive when you look at plugins and tools.
The best way for unity to make money in the business model they’ve created is to add a bunch of seemingly simple but not very comprehensive systems to the engine. Then, rather than refine these features they can wait for 3rd party developers to fill in the gaps with plugins that must be sold on the unity asset store. This allows unity to scoop up a bigger revenue stream on top of the licensing income without having to do any additional work.
It really depends on how you’re using unity. If you’re dependent on a lot of the built in components or asset store plugins or the rendering pipeline you’re going to have a hard time.
I’m sure someone will try, but it seems nearly impossible to do this in a way that’s actually useful. Most game engines are going to have fundamental differences that won’t easily map to the unity way of doing things