So, formal methods produce runnable systems, but communication remains the challenge.

If a formal spec is messy, then it's a proof of ... what, exactly?

A formal specification that bridges tech and product, that lets non-technical contributors read and discuss all the logical nuances, directly as operational code, at product's level of abstraction of interest, would transform a lot.

It's no longer a challenge to create code, it's a challenge to create business requirements and translate them into systems.