I believe this argument has been mostly refuted in the scientific community. Here's an excerpt from a Forbes article on the topic:
What are the risks of eradicating mosquitoes?
As you noticed, there are no keystone species in mosquitoes. No ecosystem depends on any mosquito to the point that it would collapse if they were to disappear. An exception may be the Arctic, but the species there are non-vectors and thus can be left alone.
Didn't know that, but there's far more out there on the topic if you go looking for the info. Bill Gates had some commentary on the topic regarding the ecological impacts not being what people believe them to be (under the umbrella of public health in Africa).
What are the risks of eradicating mosquitoes?
As you noticed, there are no keystone species in mosquitoes. No ecosystem depends on any mosquito to the point that it would collapse if they were to disappear. An exception may be the Arctic, but the species there are non-vectors and thus can be left alone.
https://tinyurl.com/5bmksuf4