Yeah, learning the grammar of what has become consensus-jazz (if you will) allows you to better play that game with other people. In that sense, I do just very much dislike that such grammar is presented under the guise of "theory" (that's both in the word and in having a pretense of explaining music rather than just being the general rules that lead to standard jazz).
Compare to cooking: if you don't know how to use a measuring cup or the difference between baking and broiling, you will have a harder time following recipes or adapting them to your own tastes. And knowing deeper ideas like the effect of baking soda or eggs or the smoke points of different oils… it can get advanced and deep, but I still insist that learning about how cooking and digestion and taste actually work would be deeply insightful to cooking even if you can get by without that understanding. Same applies to music. Jazz musicians who just memorize all the scales and voice-leading ideas and forms etc. would gain a ton by learning about what music cognition offers.
Compare to cooking: if you don't know how to use a measuring cup or the difference between baking and broiling, you will have a harder time following recipes or adapting them to your own tastes. And knowing deeper ideas like the effect of baking soda or eggs or the smoke points of different oils… it can get advanced and deep, but I still insist that learning about how cooking and digestion and taste actually work would be deeply insightful to cooking even if you can get by without that understanding. Same applies to music. Jazz musicians who just memorize all the scales and voice-leading ideas and forms etc. would gain a ton by learning about what music cognition offers.