Built our system with Dart on front and backend, and we LOVE it. Powerful language, no surprises, easy to learn. You will indeed find lots of hate for Dart all over the internet. I would highly encourage you to ignore it and explore it. Two knocks against it are the package ecosystem isn't as comprehensive as other langs, and the language itself has not been evolving much at all. There is ongoing work on an intermediate representation to facilitate the last point: https://github.com/dart-lang/sdk/tree/master/pkg/kernel
If people hate a language, my rule of thumb is, the more viciously they hate it, the more interested I get. Even if it's just to find out why people hate it, and maybe I'll find something interesting.
(And even if I find it as bad as everbody says it is, I can still pour some condescension over it and feel good about myself - Either way, I win!)
I did not dig very deep, but I completed a tutorial in all of these. Cobol was not a pleasant experience, I did the Hello World and moved on.
Fortran did not click for me, but I gave it a fair (I think) try, and compared to its abysmal reputation, it was actually fairly nice. At least for the couple of toy programs I wrote in it. Fortran 90 or 95 was a significant improvement on previous versions, as far as I could figure out. But I had no use for it either, so I moved on.
I had to learn Java during my training, around the time I had finally understood the basics of functional programming and Lisp, so I hated Java with fierce passion. ;-)
Sometime after that I took another look at Java and now it wasn't as bad - Generics had been introduced to Java, and I finally had a computer powerful enough to run something like NetBeans or Eclipse. But you know what they say about first impressions. ;-) I don't hate Java, but I am not drawn to it, either.
Sometimes, the experience is very ambiguous, for example with C++. Some people love C++, and I think I can see why they love it. Some people hate C++ passionately, and I can see why they hate it, too. It's weird. (But then, so is C++)
