One of the most important aspects in a language is how powerful and easy it is to use its collection/container types. At least that is my feeling coming from Smalltalk where the Collection classes and their rather rich protocols are used extensively and also cover String and Array and much more. If you peek into the current leading open source Smalltalk - Pharo - you can see
Collection allSubclasses size evaluate to 78. Of course, lots of those are special subclasses and not for general use, but fact remains that a strong language needs a strong library of good collections.
In Smalltalk I can for example run this:
This is actually a single method call taking two closures, one to perform a “filtering”, and one to perform a “map”. This is not a standard message in “good old” Smaltalk-80, but it has eventually been added since the usage pattern is so common. To me personally a modern language needs similar power or I would go nuts. :)