It is a shame he didn't finish it, or even continue with it. He got so much positive reception of it, and there were numerous YouTube reviewers/Let's Players trying to get involved in showing it off before he put the alpha on sale.
And then he got plenty of early access purchases.
And then nothing else happened. And that is a shame.
But, it's actually just insulting to the people who backed his product (because that's the point of early access, not just to get the game early), that he never released any info after it went on sale.
Even 140 characters on Twitter saying "I'm no longer working on Cubeworld" would have sufficed.
He owed his customers that much at least.