1) I've used the language and agree with the conclusions of the post even if I don't necessarily agree with every point.
2) I haven't used the language, but I believe open source projects must be maintained by their maintainers as they see fit.
I actually agree with both of these positions, but, having used Elm in the past for a hobby project with an eye towards using it in production, I probably won't ever use it. I loved the original promise. Evan's ideas about the Elm Architecture are worth reading and learning for anyone. But, as many others have pointed out, if one has to maintain a project over the years, the breaking changes in the language would have caused great bouts of teeth gnashing.
I don't love Java, but over the years I've come to expect that with each new major version of the language, that a small amount of work needs to be done to guarantee my production code will keep working and I can integrate new features as I have time. With Elm, every release forced me to spent hours figuring out how to make my old code work again.