donation system
You can find donation system on many platforms. But donations bring rewards to much fewer people than Hive curation. So it won't help to solve the problem you are talking about "A very small percentage of users receive bonuses".
100% upvote for curators would be better
So, you'll wait an upvote of a large curator not for a month but for a year. Don't think that would be motivating.
A very small percentage of users receive bonuses
Everyone gets rewards on Hive even those people who post just terrible posts. Hive needs numbers, so I don't complain. But you'll find no other place on the Web to get rewarded for content that nobody actually needs.
But there are problems, for sure. Hive needs better curation and needs to pay larger rewards for truly amazing content. Several dollars for a good post is nothing, should be at least dozens dollars for real gems (like on Medium).
There should "a stunning-content feed" to show strangers so that they could see that Hive is not a promise of dream, like many other blockchains which have nothing except the token and promises, but it's a living community with great content. Would be right to place that feed on the top of hive.io.
Hive needs an advertising agency (throw away a couple of projects sucking from Hive Fund, and you'll have money for that) and Hive needs more realtime events.
etc.