Context: I've written several games that no one cares about (anymore). My free games have had small happy player bases in the past. I have no real idea their reach, because last time I had a runaway hit it was passed around on physical media copies.

My tip is to play the game until you find it fun, while developing it.

Like any art, you can only be 100% sure you can please one person - yourself.

To take more advantage of the work of others, I'm now learning Lua to allow me to modify existing Luanti plugins, then eventually create my own, then eventually port some of my past games to the engine.

So there's that option as well, if you don't know where to start.