By "built-in", I was mostly talking about the fact that the literal syntax doesn't require a header. Case in point, here's some code I took straight from a toy AVL implementation I wrote a while back:

  auto children = {&grandparent->left, &grandparent->right};
  auto child = elvt::find_if(children, [parent](auto &child) {
  	return *child == parent;
  });

Yes, it's an abuse of initializer_list being a convenient "array-like" structure, but it does show that not every use of initializer_list needs to be used as you've mentioned. (In fact, I probably use initializer_lists more this way than in their "intended" way. I'm sure someone is going to yell at me some day for it, but nobody's done it yet).