key switching of sample based instruments as of 2020 requires the complete midi protocol in serial order. That is just one case. Midi users have been using this protocol for decades in myriad of ways beyond simply as a parameter adjuster for effecting notes. That includes within plugin signal chains, not just externally.
steinberg’s view on the matter is limiting users from what they have been able to do previously for decades. At this time vst3 cannot be used for midi plugin development in some cases because of this limiting point of view about the role of cc messages. For the time being, those people with the old license can continue to provide vst2 solutions, but new developers will be unable to provide certain midi plugin solutions due to steinberg’s narrow point of view about what each type of midi message can and should be used for.
The main problem is that the vst3 abstraction, though elegant from a computer sci point of view, destroys the serial order that has existed for decades in the past, both externally from the daw in virtual midi device buffer, in the midi cable itself sure but also in the vst2/au midi buffer that order was preserved and all midi events were delivered in the exact same order from the host’s event list to the plugin’s callback, and from one plugin to the next plugin in the chain of routed that way, etc always with that order maintained and every single message delivered as sent.
Vst3 abstracts all but the notes themselves and obliterates that possibility for midi users to count on all messages making it to their favorite plugin in the designated order.
Keyswitching of sample instruments with cc is one place this has broken functionality entirely.