That is not true. Autocompletion is a decision with user override enabled. It is, at the very least, a visible decision. That does not imply that it is totally automatable.
What about sensible defaults? If the libraries you use are designed with reasonable defaults that have already anticipated your needs there should not be any need for anything but the most basic syntactic autocomplete functionality (closing brackets for example) because any code at that point is customization for your specific project which is not easily generalized (otherwise it would be a default in the library).