Hi,
I am not sure about SEO exposure from TC, it certainly helps, but I would guess it is not as important as it used to be.
More quality posts wouldn't be enough imho, they should probably have/use more sub sites for what we consider noise and have the main site only talk about startups and related stories (maybe try to limit the number of stories per day, working a bit like a real newspaper in this respect). But it will probably never happen since it means less ad revenue.
Maybe it is too late anyway, I would guess the audience has changed a lot since it has broaden its topics selection, it wouldn't be considered a good judge of talent anymore, and I guess it isn't their primary goal anyway.