Yeah, up to a point, the maturity of a language's ecosystem matters much more than the quality of the language. That's the main reason I still choose Python for my web-related projects. Haskell, Clojure, Go, Racket or Arc might all be more powerful languages in principle. But in Python or Ruby, I can pretty much assume there's already a library to do anything I want to do with minimal fuss. For these niche or up-and-coming languages, not so much.
I'm disappointed to hear the Haskell toolchain is so problematic, as I was looking forward to trying Yesod.
Dont let this discourage you from trying Yesod. The Yesod team has made it really really easy to install a core of isolated packages for the framework. The problem comes from trying to upgrade. I know that sounds insane(and it is), but you should try it out, it has quite a lot to offer.
I find Python to be one of my least favorite languages in terms of the design of the language, but the one I end up using the most for the reasons you mention.
You would think by this point all languages would have standardized on a basic library. I mean, if you're not starting off with what Python (or even Mono for that matter) already has, then you're just making things needlessly complicated for yourself.
Everyone goes crazy over syntax and idioms and OMG GROUNDBREAKING NEW IDEAS (not) when really 85% of a language depends on the library and toolchain.
The differences between standard libraries, programming idioms, communities and ethos often play a large role in defining a new language, so surely sharing a standard library would in many ways defeat the point of trying something new?
A programming language is not just a spec and a syntax, it's also a way of seeing the world - "The limits of my language mean the limits of my world.", so to get a new way of looking at things, you also need to reinvent the basics to some extent, and rethink how (for example) basics like errors, threads or strings are handled.
Personally, I think it's useful to have a multipolar programming landscape, even if it sometimes leads to duplicated work, because it can give you a fresh perspective on old problems.
I'm disappointed to hear the Haskell toolchain is so problematic, as I was looking forward to trying Yesod.