I think one of the biggest problems indie game devs have is putting a lot of focus into art and polish without actually working out whether the game is fun to play. The dev gets to make enjoyable incremental progress without having to confront the difficult questions about whether the game is actually workable. Some games can get by purely on story and art, but in the vast majority of cases I think solo devs would be best served by making an absolutely minimal gameplay prototype and making it fun before thinking at all about polish.