> My conclusion is that the whole digital circuit design industry is ripe for disruption by open source, and I'm rather surprised it hasn't happened yet.

Just build a modern design rule checking (DRC) engine with parasitic extractor. That's all you have to do. I eagerly await your release on github.

I agree with you that open source really is the only valid path forward. However, you have to convince some very smart people to join your cause and they expect to be paid up front.