i am learning Elixir and liking the concepts. i am coming from kotlin/jvm and i like kotlin, apart from kotlin-coroutines. planning to migration all threading code to virtual threads. but biggest problem is threadlocal.
1. Hiring and job market - the JVM is simply more employable
2. Ecosystem - in general you can expect the JVM to have library support for most things you're going to need.
3. Typing - if you like static types, you're probably going to miss that in Elixir/Erlang. They're working on a gradual type system for Elixir that looks quite pragmatic, so I'm excited to see how that works out.
The Elixir side of things has some real advantages, though. Runtimes like the JVM are slowly adding threading paradigms that start to look like how the beam works, if you squint enough. Naturally, Elixir already has that, and already has technologies that work very well with it. Virtual threads on the JVM are a smart effort that will take a long time to be complete and will always have to take backwards-compatibility into account, especially if you're in Java itself.
Phoenix is also IMO a best-in-class web framework. I don't think it's universally applicable, but if any JVM language had something like Phoenix I doubt I'd be considering Elixir nearly as strongly (due to my affection for types). So while the JVM ecosystem is broader, it's not uniformly stronger.
I also think that "domain" is much broader for JVM stuff. The web technologies there feel pretty baroque rather than empowering, but you can still do web on the JVM, and Kotlin or Scala in particular IMO serve better for systems where the bulk of the code is internal business logic. I think that even if I adopted Elixir entirely, I'd probably retain some "second language" for deeper systems.
How do you know it? Today you have to re-assess what you've learnt in the past. If you think JVM is "simply more employable" and haven't tested the waters in last 1-2 years, chances are you're just wrong.
The feeling I have: more simpler the tech is (and JVM/Ruby/other CRUD), the highest salary cuts you're getting. And you're actually less employable.
It is that counter-intuitive, because it's one person with a coding agent vs a team in the past.