Coming from a Lisp background Julia fits like a glove in the beginning but some aspects, like the inability to redefine structs, I just crash into like a brick wall. It makes it hard to imagine writing (say) a Blender/Paraview type of application in Julia.
I suppose that Julia is heavily influenced by Scheme and Dylan but not especially by Common Lisp (or Smalltalk) where the idea of being unable to redefine types at runtime is jarring.
I wonder if Julia advocates would do better to just acknowledge that this point of view exists, even if experience with Julia might change it over time, rather than dismissing it (yes, very much so) as empty "fuss." But there aren't that many Lisp/Smalltalk hackers in the world so you can probably afford to alienate them if you want to...
You might want to try and acknowledge the other point of view where I note that, hey, we did make this work but it was a smaller deal then we thought because we legally cannot employ it in many production contexts. We're still going to work out a few details for fun and ease of debugging, but given that we have extensively looked into and thought deeply about the whole issue, we have noticed that the last little bits are less useful than we had thought (at least in the contexts and applications I have been discussing, like clinical trial analysis). That doesn't mean we won't finish the last pieces, but given how much of it you can already do and how many teaching materials show how to do work around the issues in any real-world context, and how little of a real-world application the last few bits have, it shouldn't be surprising that the last pieces haven't been a huge priority. So instead of looking narrowly at one factor, I encourage you to take a more global view.