This argument is part of a “divide and conquer” strategy, by fossil fuel lobbyists, to tell every country that it’s efforts are wasted because no-one else is trying.
Is it OK to drop litter? Individual contributions to the litter problem are small and taking your rubbish home won’t make much difference. But I hope you still don’t leave rubbish lying around. Stopping litter, or stopping climate change, needs everyone to do what’s right.
As for China in particular, it’s currently installing more solar and wind energy that than the rest of the world put together and it’s emissions probably peaked in 2024 (although, to be fair, it’s too early to be sure).