Should we stop giving votes to Diary Game posts...?

I'm in favor of deemphasizing them, which it sounds like you're already doing.

In contrast, maybe there's a way you could do something to support meaningful and unique local content that would show up in search engines. I know that some years ago, you had a local news initiative, and I'm thinking along those lines too, but I would extend that even further: write reviews of local businesses, write about public events and sporting activities in a community, etc..

For example, in the previous era of Steem - when we had apps that were intended for "micro-blogging", I ran the @rgkmb-unofficial account where I posted about local high school football games and marching band activities. It didn't get much interest on-chain, but I noticed at the time was that I was apparently the only person in the world that was writing regularly about the "Rustin High School Marching Band". Even with the lack of on-chain interest, web searches for the school brought Steemit to the top of the search engine. I'm fairly sure that Steemit must have shown up in web searches at the time for some number of people in this community.

I don't have anything specific to suggest, but maybe you could find a way to harness that general effect with your voting incentives. If people write about topics that are only of local interest, there's apparently not as much competition for search-engine real estate.