[ncmncm]

Any language built around one idea to the exclusion of others is necessarily a toy.

This is not to say that there is anything wrong with toys, as such. Toys can be educational, some very. Just don't confuse it with something that is, or may become, a generally useful tool.

This is why "pure object-oriented", "pure lambda calculus", "pure category theory", and "pure logic" languages flop. The world does not consult your language for what kind of problems it should present. The world, instead, presents all kinds of problems. Any big problem will turn out to be made of lots of smaller problems, of all different kinds generally unrelated to the sort the big problem seems like.

A useful language has what you need to address all kinds of problems. Useful languages are usually accused of being "impure" or "too complicated". They can't be summarized in a line, or a page. But there are reasons why those are the ones we use.