The species that go extinct are mostly local ones that don’t have large numbers to begin with. While one individual mosquito is insignificant to a ridiculous degree, mosquitoes as a whole, even just one species, play a much bigger role than the Northern Fuckwitted Summerbunny of East Whateverstan could ever do.
We don’t understand the intricacies of any ecosystem nearly enough to start engineering it. Pull one thread, and you might unravel the tapestry.
We wipe out thousands of species every year through pollution alone, what’s one more to add to the pile?