Sometimes restrictions breed creativity, though.
The DM can not metagame, definitionally
The secret to writing (or playing) characters that are smarter than you are is that you can take your time coming up with what they do. Maybe in-game your character has a razor wit and would have a snappy comeback for any situation. Out of game you've got a list of pre-prepared retorts you can bust out as needed.
Looking good! Those pirates have a pretty sweet setup!
Sometimes that can be fun, but only if everyone at the table is onboard for a wild tangent. If the other players are bored as shit while the special snowflake starts a unicorn breeding operation, it's time to use that No. And you, the DM, are included in that too; if your players want to drag you off to write every book in the library and that's not fun for you, you have the right to say "hey maybe you should play the game I made for you instead."
Fantasy Dexter. Actually loves murder, but instead just gets their kicks vicariously by stealing the memories of murderers
Queercoding villains to make them seem dangerous and deviant to the people of the time (and those that are still stuck in that time). Admittedly, the people making that decision probably weren't conscious of that being why they thought eyeliner made him look villainous.
What is a "domain game"?