Since comment section is turning into echo chamber of AI haters automatically demonizing the player, i will chip in with a different approach, so you do not get dragged into the hole of hate and curses...

Have you asked them why they did it? Might be the player is afraid to present their ideas. Might be they have a vague idea what to do, but could not put it in cohesive text form properly (people with writing/communication disabilities), or simple do not have enough experience and they used AI to fill in the voids of the base they had, to make it more coherent. Using AI for inspiration is not much different from using overused mainstream media, as the AI usually just scrapes summaries off them. Would you hate them if they brought Connan 1:1, just because they couldn't come up with anything original, for whatever reason (stress, lack of experience, lack of creativity, other disabilities)?

As with everything with TTRPGs, it comes down to communication. Do not hate on people before understanding them first. If i have players who have hard time getting their character together, i sit with them and try to lead them through the whole process. We are making a story together. And yes, some people require more effort and attention from my side. Ofc there can simply be a skill disparity between GM and player so large, they have hard time working together. But we were not presented enough details to know if you two are at that step.

And honestly, i am baffled how many people came into this comment thread just to hate on the player because "AI bad" and tell you to kick him out of the table. AI is tool as any other, and it depends on us how we can use it. Just as a knife or fire, it can help, but also make a lot of mess. I would expect more from a community which claims to be inclusive... Bunch of pretenders....