I think they might mean agriculturally. I have seen tomato hornworms parasitized, and various types of wasps carrying things like grasshoppers or caterpillars. So they can be beneficial.

I hate yellow jackets, but most other types seem pretty docile.

I'm curious what insects the author had in mind.

I have a deep hatred for hornets, but I can think of some other insect species I'm happy to keep in check: mosquitoes, ticks, horse flies / deer flies, cicadas, etc. And probably some caterpillars that can damage our trees by eating their leaves.

I'm not sure wasps do much for most of those. There is the "Cicada Killer" though... https://extension.entm.purdue.edu/publications/E-254/E-254.h...

Other wasps will catch spiders and use them as food for their young.

It depends on what people call "hornets". Wasps are generally pretty chill, even the stinging kind. And provide a lot of benefit to gardeners. Yellow jackets are ill-tempered and very territorial. I have no idea what benefits they bring.