An important part of SF&F is suspension of disbelief. We want, even need, the strange worlds of SF&F to be as consistent and complete as the real world is. We regard worldbuilding as a fundamental part of good speculative fiction.
Universes that are broad, deep, complete, and that follow predictable rules help us suspend our disbelief. It's the difference between "Before the Sun and Moon, the first Elves were awakened by Eru under the stars by the bay of Cuivienen" and "There are elves because there are elves, now stop asking questions!"
There are limits to worldbuilding, and those limits evolve. In the oldest of days, stories were told by mouth, and fires and paintings were the only special effects. Those stories were certainly real enough to our ancestors! Now we have 3D and digital and CG and billion-dollar movies to help us suspend our disbelief. And we regard special effects from 20 years ago as quaint and unrealistic.
There are still some limits we haven't got past, though. One of those is the language barrier. Aliens speak in the language of the film-goer, and human actors have mouths. Sometimes there are real-world subtitles, or in-universe translators. Either way, the reason has less to do with the realism of the world than the requirement to make the movie understood.
In my view, then, questions about this are on-topic and not "stupid". But I think we do need to be evidence-based about how we answer them. If there is a canon in-universe explanation, like Star Trek universal translators, we should say so. Contrariwise, if a quote from the author reveals "heck, didn't think about that", we should say that. But if what we have is really an unexplained plot hole, I don't see anything wrong with the correct answer being "that's an unexplained plot hole".
Otherwise our answers become less answers and more something like fanfic. Fanfic is great! But it shouldn't be an answer to a question on SE. I know there is no hard and fast line there, but I think that we should be careful. As Christi says in her answer, if the answer provides some good evidence from canon, that would be the right approach.