I partially agree with your statment.
As for Jax. Jax have by far better ecosystem casue u can easy use a lot stuff used in tensorflow ecosystem.
Also I’m just pointing out stuff that i didnt see in this topic and response to ckneale as is mostly hyping Julia and Flux and as a person implementing deep learning state of the art models for last 5 years of my professional life and trying a lot of stuff (Julia, S4TF, Jax, Tensorflow, Mxnet, Pytorch, Keras, Theano etc.) I’m just pointing out stuff that isnt there and can be break point for a most of the people wanting to use it in their jobs.
Julia community is living in a bubble and thats why such a cool and beautiful language cant take off for last ~3 years outside academia (ofc.), ODEs and some other small niches. It have potential to fully replace python. And few years ago there where sentiment that julia will be new language for DL, when DL community wasn’t as big and small number of people can create alternatives for fresh existing DL python frameworks but it just never take off 
“Conversely however, there is a small but significant (and growing) crowd of experienced ML users who are frustrated with how things are done in Python land and looking for an alternative.”
=> I saw same sentiment 3/4 years ago and here we are Julia ML ecosystem are still the same (ODE’s are better, very basic ML stuff is better, DL is worse by a huge margin. And even worse for Julia Big Deep Learning players are trying to move outside python but to other languages not Julia. => Facebook try Kotlin [ Paving ] and Google try Swift [ S4TF ] )