Oh yeah. Completely dead lmao. And it will never catch up to the richness of the KSP1 mod ecosystem, despite the limitations of the antique version of Unity it runs on.
I suggest keeping an eye on Kithack Model Club. It's early access (so don't necessarily open your wallet right away) but it is a very similar physics-sandbox game (minus space exploration) created by the original creator of Kerbal Space Program (Felipe Falanghe a.k.a. HarvesteR) who left Squad due to labor conditions and burnout and eventually established his own independent studio.