The obvious solution would be for Amazon to buy Bookbub. (Yes, I'm kidding--though there was a time when the idea of Amazon buying Goodreads would have seemed ridiculous, too.)
In many international markets Amazon isn't the dominant player, but its US market ebook share seems to continue growing. The estimate being bandied about five years ago was 60%, and the most recent Author Earning Report says 80%. Yes, some individual authors do really well wide, maybe even better than on Amazon, but that isn't the general trend. Amazon is also taking a bigger chunk of paperback sales. I doubt that US Bookbub decisions are driven by market share as much as by referral fees. That probably makes a considerable difference.
For me it doesn't much matter, because my experiments in going wide have never produced enough sales to even come close to offsetting the KU losses. It just isn't worth taking a huge hit on the off-chance that I'd get a Bookbub. As Juliet said of marriage near the beginning of R & J, "It is an honor I dream not of."
Of course, for an author who is doing well wide, having an easier time getting a Bookbub would be a really nice bonus.