Yes! You summed everything up perfectly! The idea of downvotes had me thinking. Telegram has downvotes. There they are used, for instance, to show that you don't like the content of the news, even if it's well written.
It should be noted, though, that on Telegram, everything is shown chronologically, but on Steemit, it would make sense to let upvotes increase visibility. I'm not sure if downvotes should decrease visibility or if they should simply show that you don't like the content.
Just imagine if there were some pretty bad news, which you felt that a lot of people should know about. Should you then upvote it for visibility or downvote it to show that you disagree? Sometimes I miss the star-based rating system from the early days of YouTube, but the more I think about it now, the more complicated it gets.
In the end, I think the upvote system now works well for visibility and payouts, and comments work well to show how you feel about the content.