The video isn't complaining about MIDI. It's just saying that MIDI isn't suitable for MuseScore's specific use case (playing orchestral scores through virtual i

The video isn't complaining about MIDI. It's just saying that MIDI isn't suitable for MuseScore's specific use case (playing orchestral scores through virtual instruments), and since VST instruments use MIDI as an interface, that problem wasn't immediately solvable. (Their eventual solution was implementing an alternative protocol and a plugin compatible with it.)