has there ever been a time when the incentive for rewards resulted in a well curated front page

Well you know probably better than I do, but I'm going to go for a solid 'no' here.

Using stake clearly hasn't worked for the main Trending page on steemit.com, other sites look better though - steempeak for one as it rotates curie/c-squared content.

I wonder if something like 'claps' or 'likes', holding no monetary value, would be a better solution to the main page - not holding my breath for their appearance just yet though.