I disagree (mostly). What's the difference between library and language built-in? PHP and C++ has a ton of built-ins. It doesn't make it less complex than using library.

Problems that look simple at the first glance are in most cases are complex with too many edge cases.

I think I have never written a single utility function that had no non-obvious bug, and imagine that in more complex problems

Not to mention in many cases any function you write is possibly dangerous.

Just take a look how many things you have to consider when checking for odd number in JS:

https://www.npmjs.com/package/is-odd?activeTab=code

And of course most of that can be fixed be using strongly typed language.