Galactus is suppose to be a peer of the Celestials who Odin and other skyfathers couldn't do much to even with prep against them. If they could stop Celestials with prep I doubt Odin could stand against him one on one. Celestials to on Asgard who had combined in the destroyer although they did cut off a celestials arm were defeated by Celestials. Thanos stood up to Odin but Thor has fought or stood against Thanos the hierarchy seems to me to be out of wack.