My understanding is before 1970, few Jazz players thought about modes. For certain, Charlie Parker, Colman Hawkins, Bud Powell, Art Tatum, Monk, etc never thought in modes.
Barry Harris shows how they did think*, a simpler, deeper way: more true to the form before Kind of Blue. Russell's Modes, inspired by a fellow patient in a tuberculosis ward, and now taught as the foundation for improvisation, seem to me a projection of Western Academic ideas unto African American idioms, with little understanding or respect to the ideas behind those idioms. Basically a "takeover" of Jazz tradition by a counterculture generation of modern Jazz players, and explainers interested in creating course curriculum. The emphasis on "Modal Theory" and scales today appears way out of porportion to it's influence in the body of recordings we now classify as Jazz.
The modal approach was used to define and frame a new form with an extreme paucity of chords. Why is it relevant to the complex progressions which came before?
Please set me straight.
ref* Alternative to modal approach: http://bit.ly/2GsJpBm