Right now, between 200 and 100000 species go extinct each year. Those are the unintentional ones, and the rate is probably growing a we climb the ladder of global warming. Even if we eradicate all mosquitoes species (around 3500) in absolute number is not so much compared with what we are actually doing without trying. And other species, less harmful, could take their spot in the ecosystem.

Yes, it would be something destructive, but you should notice the elephant in the room.

I always wondered how something like this would go: it would go on until a species of tree (or some other plant) is discovered (probably in the Amazon) that is only pollinated by mosquitoes. Well, sucks to be those trees, I guess.