I signed up to listen to Vatsim and my finding was that while it was sometimes interesting, there was not nearly enough controller coverage available. To be more popular, Vatsim would need to increase activity such that for many hours a day there there are qualified controllers at all levels at all major airports. I don’t think this will ever be a realistic expectation. AI could solve the staffing problem, and then it’s use as ATC would be huge.
But Vatsim will always be more realistic than any AI, where a qualified controller is online. Perhaps there is a way for Vatsim to use AI to fill in the gaps in coverage.