This is a meme that people constantly repeat "insects are all dead!" but I don't think it's true - these studies seem low quality. Maybe they're true in particular regions in Europe and North America.

As a counter-anecdote, I bought a house recently and the back yard is basically uninhabitable all summer due to insects. Insects may be less prevalent along some roads due to better drainage.

Another point I'd make is that there's no reason to think insect life should be stable across 30-40 years. Insects are not people. Even aside from climate change, insect population is very dependent on weather patterns.