The constellations do change over time. But not due to universal expansion, but rather because, like everything in the the universe, the stars are in motion. We can’t notice any changes during the course of our lifetimes, as it takes thousands of years to become noticeable.
Universal expansion occurs on the grandest of scales. ie, even structures as enormous as galaxies, with hundreds of billions of stars contained in them, basically aren’t affected by cosmic expansion. Gravity wins out at even that scale and holds them together. UE takes place in the incomprehensibly large regions between galaxies.