Oh yes, regular folks in the Imperium are absolutely forbidden from knowing anything about or even talking about chaos at all. The guard may even be sent to fight chaos directly without being told what they’re fighting or why, just that they are fighting heretics. And if they ask for more information they will be made an example of so nobody else thinks it’s a good idea.
The Imperium is not a nice place to be, mostly
I do the opposite. I will run any game EXCEPT D&D. This gets people to try new games, and if they really wanna do D&D they can do it themselves, learn how to DM and run a group, and then I get to play. It’s been a pretty flawless strategy for me overall