Agreed, that isn't the reason JavaScript in particular was essentially motionless for about a decade. As you note, that was largely due to political factors and

Agreed, that isn't the reason JavaScript in particular was essentially motionless for about a decade. As you note, that was largely due to political factors and disagreement about language direction among the various competing implementers. But compared to say Smalltalk, Scheme, and Lisp, I think Ruby and Python have been able to evolve incrementally in part because of their simpler more hackable implementations.