You think the Empire can just "suppress" TRILLIONS of memories of the Jedi in 30 fucking years? This is why you are an idiot and people like you are why they can successfully peddle the EU garbage they do.
It was never made precisely clear what the Force is to the common citizen.
Religion: a set of beliefs concerning the cause, nature, and purpose of the universe, especially when considered as the creation of a superhuman agency or agencies, usually involving devotional and ritual observances, and often containing a moral code governing the conduct of human affairs.
Does the Jedi follow a religion or a code? Shaolin monks, certainly one of the inspirations for the Jedi, we could call that a religion. Bushido for the samurai? It operates within the same mythological constructs as Zen Buddhism and Shinto but I don't know if it in itself constitutes a religion.
Regardless, we do have plenty of examples in our own world of governments trying to stamp out religions and superstitions. China's had a miserable time with the Tibetans and the Falun Gong. The Soviets tried to stamp out Christianity but we still have the Russian Orthodox Church. People kept the faith despite several generations of official suppression.
Perhaps Imperial propaganda tried to explain away Jedi abilities as tricks and artifice rather than actually drawing upon an energy field existing throughout the universe and all matter. Maybe the accusation is that they're using advanced technology to simulate the appearance of magic to con the rubes.
You might explain Han's skepticism as sheer ignorance like denying the moon landing but we also have the example of the imperial officer mocking Vader to his face as if he's never seen the Sith choke a bitch before.