Thomas Shey
Legend
To be fair, that's not just the responsibility of the GM. When it is another player's spotlight time, you need to stay engaged. And when it is your spotlight time, you need to work toward making the scene engaging. This, more than Mercer's GMing or anything else, is what CR excels at and serves as a good example.
But, yeah, if the GM's game is boring, let them know (preferably diplomatically).
I don't even think people should require to be engaged during other people's spotlight time except to the degree they need to do two things: 1. Know what happens to make decisions with their own character, and 2. Be ready when called on to be able to act. I don't see any point in pretending in interest in parts of the game that don't interest me; that just says you can't have people with different things that interest them.
Basically, I don't feel its other people's obligations to interest me, but neither do I feel its my obligation to feign interest when its not there.