MIDI is very slow and has a very limited message set. There are better alternatives, like OSC, but it seems like the chances of the music industry collectively acting in its own best interest again and approving a new standard are very slim.

Well, the biggest limitation is that it has granularity of 0 to 256 for message data.

That means if you want an analog like continuous change from 0 to max for some audio property, you get stepping instead.

It's also not very fast for todays work with tons of channels.

I doesn't know about audio at all, etc.

OSC is a better replacement, but not widespread enough.