First, they aren’t critical in either of those roles, and second, there are a few thousand species of mosquitoes, and only five of them cause issues with human health. Get rid of those five, and you haven’t caused much ruckus. The others will be fine in their continued parts.

Now, that being said, nobody knows for certain what will happen if all five are completely eradicated, but the sentiment above seems to be the consensus among people who have studied them.