High grimoire means you've played a lot. You can play a lot and develop bad habits and still be a poor player. I have 600 hours invested into crucible but I'm a negative kd scrub. Time invested doesn't mean you will be good at something. Sometimes people are great starting off and don't require much practice and other people just stop improving after time.
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You can invest all the time you want in Crucible and still not get the wins. Your Grimoire wont go up until you get that win. So time played = time played. Grimoire =/= time played.