It can’t be a satire until there’s a real alternative shown to the empire, at least hypothetically. Not while there are things in the lore that actually ‘justify’ a fascist response. Not until every rebellion stops being chaos or genestealers.

You should play 40k Rogue Trader then, and just take the Iconoclast options all to their logical conclusions. I would rather not spoil the effect of it, but I can DM some good outcomes if you like.