It's hard to express to people born after ~2005 or so how many insects there used to be. Even in cities. All the time. Everywhere. Swarms of gnats in the air during the summer. So many fireflies that it was disorienting. Couldn't drive even on an urban highway in some places during spring without apologizing every five seconds because a butterfly splatted on your windshield. Actually, just having to constantly clean your windshield from bugs in general.
Yeah, the mosquitoes sucked a lot. But there were plenty of other things too, including birds that ate the mosquitoes. Now the same birds don't come around because there isn't enough food to make it worthwhile. And there were toads out and about, all the time. In the middle of urban areas! Now I only see them close to natural parks. I'm only in my early 30s, and the decline I've witnessed in my lifetime is staggering.
A lot has contributed to this: urban sprawl creating habitat fragmentation, pollution in general, global warming creating climate change which shifts weather patterns away from what insects in the area are adapted to. But the absolute worst thing we've done (wrt insects) is pesticide use. We never needed to use pesticides in urban lawns (we never needed to have lawns in the first place). People are so afraid of insects that they would rather wage a forever-war with chemicals rather than cultivate a healthy ecosystem to more efficiently limit the populations they don't want.
And then cities started conducting aerial spraying for mosquitoes, which hastened the collapse of everything else. People will say "this pesticide doesn't target those other insects", but fail to understand that you can't just pull at one part of an ecological web and expect the rest of it to stay intact. Everything is interdependent. If we want to build a just future, we need to remember and honor reciprocity.