Making original content that is also interesting/fun is really hard. Everything has already been done, only better than what you have.
The bigger the game, the more stupid little details you have to deal with. The more parts there are the harder it is to make everything work cohesively. It’s a never ending cycle of fixing things then fixing things you broke from other fixes.
I’ve gotten better at recognizing errors and how to fix them. After getting the same ones you start to get a sort of”muscle memory”. I can actually read them and figure out where they came from instead of having to constantly google them
Find unbiased feedback. For example, I have a friend that hates mobile games and I had him play mine to have him point out everything bad about it(which was a lot). Most other people close to me would just say ( iTS sO fUN!)
Watch people play. If different people are getting stuck at the same place where they don’t know what to do, it’s not intuitive enough.