The answer is simple...

Get rid of curation rewards

But how in the world could a social media platform ever suceed without paying people to upvote?

I don't know... maybe how youtube, facebook, reddit, and everything else has been and continues to.

People should upvote content if they like the content. It should be as simple as that, but as it is the choice to upvote or not is far more complicated and it seems to be continuing to get more and more complicated in lieu of the recent 0.14.0 update. We now have voting sliders for god's sake.

The current curation rewards punishes upvoting posts you like and rewards upvoting posts that are predicted to be popular before they become popular. And the more steem power you have, the greater that punishment and reward. You can't vote on a post that's less than 30 minutes old, and you can't vote on a post that's more than an hour or two old if you want to maximize your rewards making any post made at down times of the day even more doomed.

What posts are predicted to be popular? Posts made by big authors who have a history of making high paying posts that are about one of the few mainstream topics. Certainly not posts on unpopular topics or posts by minnows. It is absolutely crushing towards the diversity of content and the distribution of steem. Even ignoring the problem of bots, the current system has to go.

Bots are always going to be better than humans at this arbitrary game

They can be online 24/7, search through every single post, look at the full history of every author, automatically vote at the best times, etcetera, etcetera. It doesn't matter if you limit the target number of votes to 5 per day, humans are not able to compete and no one is going to want to join a site ruled by bots. The answer isn't to keep adding new rules, making the system more and more complicated and ridiculous over time, it's to remove the silly game. Bots are and will be made and used to play the voting game in order to maximize curation rewards. Getting rid of curation rewards will put an end to these harmful bots.

But then less people would vote

It's true that less people will vote when no one is paying them to, but the same amount of steem is generated and redistributed everyday regardless of how many people are voting. The more whales that stop voting, the more voting power the minnows will have. We'd be losing quantity of votes but gaining massive quality. And since curators aren't earning anything, that also means significantly more will be paid to content creators.

Just imagine, if you could freely vote however much you want, whenever you want, on whatever you want.