Gear grinding has nothing to do with P2W because everyone has to put in the same amount of effort/time in order to acquire the gear. With P2W however, some people might have rich parents who give them plenty of cash, while other kids might not be so lucky. Some people might make minimum wage, while others might make $100+/hour. This is why it's unfair to have P2W. Time on the other hand is the great equalizer. Everyone has the same amount. No more, no less.
Everyone has the same amount of time huh? So the guy with a full time job has the same amount of time available as the unemployed people that can play all day?