Milkweed is the only one that can feed the Monarch at all stages of its life, from larva to caterpillar to butterfly. When people plant butterfly bushes, it “tricks” the butterfly (or at least crowds out better options) into laying eggs where the larvae will ultimately die of starvation.
I get the sentiment but tend to I disagree. Maybe some very specific species might benefit somewhat, but in general the principle makes little sense. Whatever native fauna there is in your area spent thousands of years in relationships with other native flora and fauna. So not just plants, also the soil life, the combination of plants, the terrain variation and so on. Hence replicating that as close as possible should be what works best. Which a far as nectar/pollen goes means not a single species but a combination providing it throughout the seasons. Whereas 'long blooming and nectar rich' completely ignores specialist insects which only get nectar and pollen from one particular species or group of species, insects laying eggs on specific species only, and so on. Butterfly bush is considered a McDonalds for insects, and that's actually a pretty good metaphor. Red valerian is in the same ballpark.