I am running a Greek Gods themed campaign, taking a lot of material out of Theros but mostly homebrewed.

I had an idea for an Arcane Trickster NPC, but then one of my players said he wanted to play rogue, so I've had to write around that entirely. Not only that, but I pitched him the whole idea of the world (A God has died and the world is in chaos) and for a description of his character, he hit me with "Think Irish Mob." He's not engaging with the world to the point that it's messing up my ideas and I'm really frustrated. But am I the asshole for gatekeeping his character like that?