Hear, hear.
Haxe is very much underrated. You can write mobile, web, server, system, embedded, game code with the same programming language and deploy on almost whatever you want. Guess Erlang is the one target missing.
It's a nice language and it's mature as is it's toolset. It's very trivial to integrate native libraries.
I believe it's underrated (what people most often say) because of the libraries which are kind of a mix of quality and a lot of them outdated and unsupported. HaxeFlixel/OpenFL are very nice and stable, but that's for a limited audience. Myself and others using Haxe, I believe (but I have nothing but experience to back this up), just integrate what they need themselves because it's easy. And never release it because it's not good enough or release it half-baked (to the point they need it).
I never wrote anything in Flash and so I don't really see OpenFL as anything Flash (while it obviously is); it's just a nice, well documented API for me.
Edit (bit offtopic):
Another underrated language that manages quite a bit of targets quite well is Monkey-x; it's also targeted at games. I wrote a few production games in them and it's nice to work with.
And yet another one, which I really like, is https://mercurylang.org/about/backends.html ; the implementation is very nice but really complex. That makes working with it harder because there are not many people to support it. With Haxe / Monkey I can fix things myself, with Mercury that's just really too much work.
Almost the opposite of that one is Shen which, again, has many languages it compiles to / runs on for which building targets is rather trivial. It's actually the only language of all the above for which implementing a new backend is trivial.