I've read a few things about this issue and I'm not entirely sure how I feel. There are a lot of alarmist comments and articles, and people who don't understand what is going on because of them. This is going to be a stream of my thoughts and things I've learned, not really arguing for any "side".
The main problem seems to be with honey bees, and in North America. Honey bees are not native, or wild. I believe they are somewhat inbred or at least have a founder effect. And they are transported around the country every year by farmers, spreading whatever pathogens they have to every colony rapidly.
We also steal their honey (and breed them to over produce it in the first place). And in some cases replace it with shitty substitutes like corn syrup. But I'm not a beekeeper and I'm sure they know what they are doing, but still. It's not a very natural environment for the bees.
There are native species of bees. E.g. bumblebees. I do not know whether or not they are declining. I found a single study about their long term population. Some species are declining, but others are not. I am very confused about this result and don't know what to make of it. These bees have an advantage being native to this environment, having more genetic diversity, and not being vulnerable to the same pathogens.
It's not clear if native bees would be able to take over for industrial agriculture, which is optimized around honey bees.
The actual number of honey bee colonies in the US has not declined, despite these issues. However this may be due to intensive efforts by farmers to keep them alive, and operating at a loss. It might not be sustainable.
It's not clear if insecticides are really to blame. Since the insecticides in question have been around for a long time before this was an issue. It's likely a contributing factor though.
Mostly this affects the fruit industry. Most staple crops, or at least grains, do not require insect pollination. Humanity is not at any risk of starving to death, even in the worst case scenario.
Honey bees are actually super inefficient. In a farm in China, they died off, so they had to pay humans to pollinate all the trees manually. Production increased by 30%, since the bees missed a lot of flowers. While paying humans is a bit expensive, it's possible technology could replace the need for honey bees and improve agriculture.
On that note, we could also replace insecticides with better technology. E.g. insect zapping lasers, or robots that seek them out. Chemical pesticides are really really awesome, contrary to popular belief. But they do seem crude to me.
And GM crops have literally nothing to do with any of this. As far as I can tell. Glyphosate is a herbicide, not an insecticide.