It's my understanding that ecologists generally agree we could eradicate human-biting mosquitos and it wouldn't cause any real problems. Yes, other species eat them, but they're not a critical species in any ecosystem, apparently.

You know how there's those stories of scientists introducing a species into an ecosystem for one reason or another, and all sorts of unintended consequences happen? Ever notice how those stories are all from around the 1950s and earlier? It's because we actually got pretty good at thinking through all of the possible significant impacts. We only introduce/eradicate species now when we know doing so is a good idea and have worked through the consequences. But I want to be clear that I agree with your sentiment. You shouldn't intentionally change an ecosystem without serious planning and consideration for what will happen when you do.