Eumenes fraternus on Allium flowers, Eastern Nebraska

Yes, most wasp species are good pollinators since adults are generally nectar feeders. They're not as efficient as bees since they're not as hairy, but they pollinate a lot nonetheless. Some wasps are actually specialist pollinators for certain plants (see figs and fig wasps). Wasps also serve other important roles, including population control for other arthropods since they hunt and parasitize them.
Wasps are also generally very non-aggressive. Hornets, yellowjackets, and paper wasps give the rest of the wasps a bad name, but a large amount of wasps can't even sting, and another very large amount can sting but are very non-aggresive (solitary hunting wasps are a good example of this). I'd say even paper wasps are really non-aggressive unless you get too close to the nest, and they just tend to make their nests close to where people often go near.