I don't think the male default is a non-issue because the male default is a thing. Like, not a Smash Bros thing or a video game thing. There are numerous languages where that's how things are structured - even in Japanese which doesn't have grammatical gender like Spanish or French, a boy is "few years" while a young girl is "few girl". So it doesn't strike me as particularly unfair or pedantic to say that Smash Bros is contributing when it has an overwhelmingly male character select screen and buries the women as options, then says that's good enough.
However, I don't think it's necessarily for lack of effort on the part of Smash Bros that this happens, as this can also come from the pool that Smash Bros is drawing from. The whole concept of of Smash Bros is about pulling from source material, so if the source material is falling on the male default instead of flipping a coin, then that's likely going to be reflected in Smash as well.