Right, but that's not how science works. You need to exhaust all possible explanations before jumping to wild conclusions.
You don't say, "What's that in the sky? A UFO? Must be aliens!" when there are hundreds, of not thousands of possible reasons why an observer is unable to identify an aerial phenomena, and none of them involve aliens from another galaxy sent to visit us.
I would also hesitate to automatically rule anything out. The Fermi paradox exists for a reason, and it makes logical sense that if life can appear in one place, it can (and will) do it again. In a universe as large as ours, it's basically inevitable that we will eventually discover some form of alien life, even if it's just single-celled organisms (assume we as a species survive long enough).
I just wanted to throw my 2 cents in because whenever anything like this comes up, you get a rush of two kinds of people: "omg aliens!" and "omg look at all the idiots who thinks it's aliens; everyone knows aliens aren't real". It frustrates me because the existence of alien life shouldn't be controversial. If anything, imo, the idea that alien life doesn't exist should be controversial (the Fermi paradox exists for a reason). Just because we haven't seen it doesn't mean it doesn't exist. It's honestly scarier imo if it doesn't exist due to the implications of it.
--- someone who woulda probably been an astrophysicist if they'd been given a chance earlier in life
i said nothing about aliens, all i say is that claim "dimethyl sulfide = definite sign of life" makes it a powerful clickbait, because there are processes that can provide it abiogenically from something similar to earth's primordial soup