My understanding is that Mixbus used to be special when it was the only game in town that could do inter-channel plugin communication to simulate a mixing desk in front of you where the channels push and pull on each other. Inter-channel plugin communication from VST to VST is still rare, but it’s happening from third parties now so it doesn’t need to be a DAW feature so much any more. Airwindows console 5 I think is their latest, and it really does a good job of doing some light saturation and some non-linear summing on busses where what’s happening on one channel can have an effect on all the others.
Brief primer on inter-channel communication: Most console emulators simulate a single channel in isolation, but then when you overload the adjacent channel, nothing happens. With inter-channel plugin communication, the overload of one buss can saturate others as well, etc.