[PaulDavisThe1st]

Logic does actually use auval these days, so things are improving. But this still doesn't catch the cases where the issue is something that auval can't or doesn't test (e.g stuff related to GUI interaction).

Plugin API design is an art, indeed. There was recently a brief bubble of activity on KVR among a number of independent plugin devs who found many things to dislike about VST3. A long discussion ensued, there was some talk of picking up LV2 instead, then it all evaporated and nothing was left. The last time the industry tried this was in around 2003, and nothing came (directly) of that effort either.

[lavabiopsy]

That's also another aspect where the plugin API vendors have not much incentive to fix things, because users can just use another thing on top of it (JUCE, DPF, etc) that makes better progress towards solving these issues from the developer perspective, but still DAWs are left with the tractability problem for other plugins that don't use that.

To me, if there is any interest in solving that, I would just expect someone to put a new plugin backend in JUCE/DPF that is specific to the DAW and then compile that together with the plugins into a big giant build. That's more what I mean by "dropping plugins", it's how you avoid the MxN problem too. But I think that many DAWs (including Ardour) gain little benefit from doing this at this time, so if that was what your original sentiment was, I agree.