WhatsApp, Facebook Chat used Erlang, and Discord is still using Elixir… make of that what you will, I suppose.
And Ruby / Rails + your frontend of choice is still a ridiculously productive stack to bring up an app, and probably run it at any scale you’re likely to realistically hit (poster child being Shopify)… if you ever get to stage of “scaling problems”, you are at a stage where you’d be rearchitecting parts of your stack regardless of what your original implementation was in.
So in sum, choosing a particular language because of popularity, I think, is not particularly useful framing. I’d say, choose one because it either gives you joy to write in and maps to your thought process well, or because it has a particularly strong ecosystem for the subject matter. Life is too short to program every day in a language that you dislike just because you think it’s the “safe choice” :)