Constraints are necessary for ingenuity and creativity too.

Also, those constraints create consistency though necessity. For example, you can write immutable code in Javascript/Python/Whatever, but because it doesn't force it on you through constraints of the language, you have no guarantees that other parts of the application follows your immutability rules, so many of the benefits are lost. Being able to make assumptions about a program, because the language enforces them to be true, is very useful.