You are correct in that  netting will interfere with pollination from insects but some plants can be hand pollinated and some crops can be pollinated by shaking the plant to distribute the pollen. The most practical way is to remove the plant covers on sunny days between 10 am and 4pm when the crop needs to be pollinated. This would be when you see blossoms. On cloudy or rainy days less pollinators will be about so you can keep  the crops covered.  Once the crops have fruit you can leave the covers in place as pollination would no longer be needed. For potatoes and cucumbers leave the netting in place on young plants and seedling and remove it only when you see that the flowers have been produced. Some insects may sneak in as well but because the plants will be older they will not be harmed as much by a few insects. Keep growing, Marianne Binetti