I'm not sure why you're grouping those four languages as they overlap very little. Go has latency and emphasizes network bound services (and randomly docker for some reason, I'm sure a good one); rust is a c replacement; swift is for writing iOS/Mac apps; and crystal is a newborn. I'd actually call it quite close to go: a high emphasis on concurrency and services. Single thread performance matters much less when scaling horizontally is mandatory to smooth latency spikes, and I'm betting on io bound work erlang would be competitive with go.
I've never used elixir but I assume it has a similar performance profile to erlang as it shares the vm.
I actually had assumed it was cross platform but there was no reason to use it.
I certainly wouldn't invest my code anywhere near Apple unless that was also my market. Who knows what direction it's moving, aside from in Apple's interest. I'll stick with rust and go: between the two I get everything but easy objective c interop.
Plus, their design decisions with respect to null ability is... Interesting. It's gonna feel gimped by legacy needs for a long time.
I listed a few examples of emerging languages to clarify that Elixir is not in the same class when it comes to computational performance on a single machine. The performance profile is indeed Erlang-like.
Keep also in mind that my reply was within the context of a thread on Crystal. OP sort of sold Elixir as a fast language that we can use now while we wait for Crystal to mature.
My point is not that Elixir is useless. My point is that we must not oversell Elixir as a fast language. Generally speaking, it isn't. It excels at horizontal scaling, which is great, but I wouldn't call it "fast" without proper qualifiers.
I've never used elixir but I assume it has a similar performance profile to erlang as it shares the vm.