What ended up working during the late 80s and through the 90s were ASICs that could be reused in areas other than just "pure" synthesizers - digital pianos, home organs, PC soundcards (IIRC both Emu and Ensoniq ended up being bought by Creative, the SoundBlaster company).

So this worked out well for those companies that were in a position to do a good job of both the ASIC and logic board development, and also use the resulting technology to address those broader markers - Yamaha being the pre-eminant example. (I agree with the point about the DX7 being a sidenote, but I'd say that all the other product lines that the tech eventually flowed into will have ended up being rather more than just a sidenote.)

Regarding the current market, despite all the retreads, I do think there's more interesting stuff going on than there has been for a long time (certainly in comparison to the analogue synth revival of the 90s), and I hope that manages to continue happening, even as I also kind of hope that the retro-appeal stuff will simmer down a bit.