craftsmanship was at an all-time high in the 70s. some people felt that it was at the expense of "heart," though... which might be why everything exploded by the end of the decade with punk and hip-hop, where not being able to actually play an instrument was something to be proud of.
Curtis's sundtracks: i son't think he saw them as "moving on". to him, it was an important part of his work. and he remained true to himself throughout. like with Superfly... he felt the film glorified drug culture, so he secretly implanted messages in his soundtrack that subverted this perceived "negative" message. he still maintained all his values through those soundtracks.