This seems a bit straw man. "Distributed systems suck because Developer B has to wait for Developer A to add stuff to System A so System B can have a new featur

This seems a bit straw man. "Distributed systems suck because Developer B has to wait for Developer A to add stuff to System A so System B can have a new feature". What you have there is a totally different problem that is unrelated to being distributed or not. Replace the word System with Module and imagine they are in the same codebase, still have the same problem. This post smacks, distributed system are hard and gave us a new set of problems that seem hard, runaway!