This is such a common gripe among non-scientists about science, and not only does it demonstrate 1. That you don't understand the purpose of science, but also 2. that you've spent zero time attempting to understand why someone would want to study "obvious" things, because this complaint is so prevalent that numerous scientific communicators have put effort into explaining why this seemingly "common-sense" belief is actually counterproductive. So like, the answer you see is in front of your eyes. So then I ask, is this person making an effort to know or do they just want to complain and feel superior. Wanting to feel superior is very human, I can't fault you for it, but consider spending some time trying to answer, "Why do scientists study obvious things?" next time, before deciding something is dumb.
That aside and onto a different point, some of the most fascinating results of science have been researching "obvious/stupid" phenomenon and getting surprising results. But.. as stated above, all of that information is out there and you seemingly evaded it all this time, so I'll stop there. I hope you'll use this as an opportunity to seek out information next time instead of spending your time to construct a complaint, the world is a much more enjoyable place when you approach it with curiousity instead of judgement.
I wish you the best.