We don't see the swarms anymore, because they are all dead. If you don't look, you will not notice -https://www.science.org/content/article/germany-s-insects-ar...
AFAIK a nonprofit in Germany collected real data over the last decades. Your childhood memories of windscreens full of insects after each trip are true
> Your childhood memories of windscreens full of insects after each trip are true
I think cars became a lot more aerodynamic which makes comparisons difficult.
When I installed a roof rack on my car, it was full of insects after a trip. I don't know how the amount of insects would compare to decades ago though.