How come we don't really see anyone worshipping or venerating Arceus if it's the God of the Pokémon world? I mean it has what, Volo's obsession and I guess Cynthia also has a passing interest in the Sinjoh ruins event but that's about it really.
And no, it being a Mythical is not a reason, Celebi got to have a shrine in Ilex Forest.