It's nuanced because it could reduce suffering overall, but it could also disrupt ecosystems in ways we can't predict and cause even more suffering. I think the latter is more likely. People have a tendency to paint animals they don't like as insignificant to the ecosystem, but they're nearly always incorrect. Wasps, for instance, are important pollinators, even if they do sting, and mosquitoes are an important food source, even if they are deadly. Anyone who advocates for eradicating species like these is doing so through a biased lens. We are nowhere near the point, technologically or scientifically, that we'd be safe playing god with the natural world like this -- especially not with the massive damage we've already caused to the environment. Someday? Maybe. But not right now.
I do also find it horrific to forcibly alter a mosquito's body so she can't express her natural behaviors. After all -- mosquitoes may cause harm, but they lack the capacity for moral reasoning, and thus cannot be evil. Thus, they don't "deserve" any kind of torment. But my personal discomfort with this isn't a moral argument.
So, uh, that's my take on it as a vegan.
Though it didn't "crash" any ecosystems, DDT still accumulates in the environment, where it remains for a long time and causes ongoing harm to insects and the animals that prey on them. Though the most problematic use of DDT by far is in agriculture, its use against mosquitoes isn’t exactly without issue. Not to mention, mosquito populations can become resistant to DDT, requiring more of it to achieve the same effect.