OSC is fantastic in many ways, but it makes for a pretty inefficient (and unnecessary) replacement for the primary use case of MIDI, which is note on/off messages. It’s much better suited to some of the other layers that got bolted on top of MIDI, such as MIDI Show Control. For most musical purposes, MIDI v1 is perfectly sufficient, well-documented, optimized, and open (from the standpoint of being free to implement).

OSC absolutely has caught on in a lot of professional applications, just not the ones that MIDI was initially designed to serve. It’s huge in the world of theater, for example.

(Background: I wrote the initial OSC implementation for QLab [a theatrical show control application].)