I got a C&D 1h after reverse engineering Serum 2 into an Open Source alternative

Honestly, what were you expecting? You pirated their app. It would be different if you didn’t use Serum as the direct source and the app didn’t look exactly like Serum.

The software wars have officially began

Good.

Serum is a cool and very reasonably prized synth, and you‘re just pirating it.

No, your AI-washing does not count as an independent reimplementation.