Universal truths indeed.
Content quality is hard to measure but i would still not dismiss it in place of social value..

The outward perception of steem content isnt based on social value offered by steem creators for steem users. Its based on general wider perception of what quality is.
Thats why i would put quality in front of social value in all cases.
Thats why i think that each well earning steemian should diversify content in a way that

1. Creates with intent of creating content with positive outward perception. That is what attracts those that consume content.
2. Provides social value to the platform.

I try to diversify my content in that way to higher or lesser success.