Ours have gotten more pleasant as we've fostered umbellifers (plants with big pads of flowers, like those in Apiaceae (like carrot)) and other large flower displays made up of lots of tiny flowers. The busiest seem to be pepperbush (Clethra alnifolia), New Jersey Tea (Ceanothus americanus and my favorite plant), and boneset (Eupatorium perfoliatum). Yarrow (Achillea millefolium) is usually pretty popular as well - if these are native or naturalized to your area they'd be a good way to lower the competitive pressure for food sources, which makes many wasps way less pushy. If not, I hope you're able to find some locally adapted species of plants to fill this niche.