I don’t adopt Crystal not because of some JIT, but for me, Ruby typing and it’s community are better.
This is only my personal preference but, Crystal take away productivity features of Ruby namely duck typing/dynamic typing.
Ruby is more productive because it allow partially incorrect code to be executed, and the REPL let’s people test their assumption in small chunk leading to bug free end product, the reusability of libraries are by far greater because of its typing. (For instance, I don’t use ActiveRecord but ActiveModel let’s me leverage all gems that support ActiveRecord)
And even with some library binding from the community, the official support from tech company isn’t there. (e.g. MongoDB)
The only thing Crystal seems to better than Ruby is the concurrency stuffs.
My context is, mostly, I’m working on an enterprise software. My opinion may changes if I use Crystal in some other area.
JIT or not is not a deal breaker for me.