Considered as purely a syntactic issue there's not much for discussion. Fix the parser. But! Conceding that method/function application is useful along side the invocation operator `()` (which it certainly seems to be) makes this an interesting semantic issue. That is can two terms mean different things but look "similar"
I have no interest in telling anyone how to build a programming language or that one approach is subjectively "wrong", but knowing that certain term pairs in a language could be ambiguous with respect to each other seems like valuable information. Provided to the creator at the right time it might help with language design.
For what it's worth, this particular ambiguity was discussed as part of the original language design. It was decided that having parentheses for both argument definitions and argument application was useful parallelism, and that function literals shouldn't have to have a "def", "func", "function", or other prefix. From those two ideas:
(input) -> output