Erlang's advantage is being able to build a featureful, secure, scalable and performant enough communication backend in very little time and effort. This is a niche in which it can not be beaten.
You have a very naive view of large-scale distributed systems. For companies that truly need them, "time" and "effort" are never a consideration. Furthermore, the challenges facing these companies in battling project delays and cost overruns are the 100% organizational and political, not technical.
I'm not sure that's true. Sure, a few of the most famous software companies in the world have built their own at considerable cost. But numerous other huge, important companies are dependent on large-scale distributed systems whose major drawbacks (reliability and maximum scale, usually) and major benefits (simplicity, time/resources saved on not having to hire tons of specialists, quick development time) are based precisely in the time and effort constraints under which those systems were developed.
My entire intention was to say Erlang is easy to get off the ground with quickly.
Most companies outside of the Silicon valley bubble are resource limited.
a) Erlang (as opposed to something else) is only useful for large distributed systems.
b) If your organization is at the scale where you need a large distributed system, then the problems in your project aren't related to code or to coding speed.
b) Needing a large distributed system is a requirement that one can get to from lots of situations. You are making way too large of a generalization.
b) No. Large distributed systems is not something you stumble onto, it's a result of many years of organic growth.