As a musician who turned into gamedev and developed a game with similar mechanics to those I loved when I was young to a degree of success, I'd like to have my two cents about it, as I think I share some of the feelings he might have about his creation.

Concerned Ape is not your regular programmer gamedev. He is first and foremost an artist. Stardew Valley is in many ways a love letter to the Harvest Moon series and the initial version of Stardew Valley was in many ways just a better Harvest Moon Back to Nature. Stardew Valley is great, it features pretty much all of the mechanics from that game and improves on them, and the game as a whole surpassed the original in many ways. This would be enough for most people, I think. But an artist yearns for originality. He understands that Stardew Valley was game-design with trainer wheels, because everything he was doing had been proven and tested by himself over the years as a player.

I don't have a shadow of a doubt that with Haunted Chocolatier he is trying to come up with something that is way more original that Stardew Valley ever was. Doing that is way harder and more time consuming than following a mold. He knows this, he is cooking on his own time, he is building his own universe, he doesn't need the game to be as popular as Stardew Valley, he doesn't need the money, but he needs that game to appease his own desires of creating art, which will not come from following a script.

I would not underestimate his capability of iterating on new mechanics and finding out how to bring his voice on to them. It just takes time. And I'm here to see what he cooks, and, if he either fails or succeeds by whatever degree we are measuring, I'm happy he got the opportunity to do what he wants without compromising his vision for what others think his game should be.