I wonder if punishing presence of advertisements would filter out most pages that are SEO'd to the max and instead promote "labors of love" type pages.

This is an interesting idea because it would create a type of non- or anti-commercial SEO that could counteract the commercial one. However, Google would never do it because they sell most of the ads that would be (not) hosted on these sites.

Google owns the largest online advertising network though, so that’s definitely not where their bread is buttered.