If you're really serious you go C or C++, not interpreted languages at all. But that said, plenty of big scale stuff is running on PHP, Python and Ruby. The language matters less than the people using it and the architecture design.
In my experience Haskell also neatly address the other two points of people and architecture: the average [0] level of skill of developers in the Haskell community is higher, as is their average level of grit and determination (because of the learning curve). Haskell almost encourages constructing your applications as operations over streams of events (a la event sourcing, unified log etc), which for my money is the best way to think about designing most platform type apps right now.
[0] Note: I'm not claiming that all Haskell developers are coding ubermensch, just that the average level of the pool of talent is higher.