I'm 17, recently had a similar experience to what you describe. As others have mentioned, and from my own experience, this may indicate they are avoiding a much bigger problem. If there was a bigger problem they're trying to avoid, do they trust you enough to tell you? Would you truly listen and support them, or would your immediate reaction be against how they feel and in favour of _your opinion_ on "their entire future life"?

Aside from your perspective on their grades and time spent gaming, you don't list any other details...

If you wanted to discuss this in more detail with someone younger feel free to reach out, happy to chat.