Most of the time, you - as an indy developer - will not be able to relay on big institution measuring the player acceptance your game. You may even not know what your exact userbase is.

So, we need an easy to implement way of gauging how well the difficulty level of your game matches your user group.

A well suited way to accmplish that is to use an analytic tool, or even better, using an global highscore system.

If your game fits the highscore conecpt, you may plan with a global highscore system right from the begin. This way you add additional challenge to the users because they can compare their own skill with the skill of other players.

If you look at that from a distant point of view, you will find, that even the popularest Role Playing Games rely on that concept: The challenge is to beat other players.
We all know, that this key concept does work. They only differ in the way you can raise and built your skill and in which manner it comes comparable to other.
Most of the time you will find, that players have some sort of competition or contest against each other.

Back to the point: If you have a global highscore system built in, you can just look into the recent and overall scores to find out which mode of your game is played the most often and at which level the most players have their highscore.

If you have a game with - say - 10 levels and most of the highscores stopped at level 5, it is possible that either most of the players were not able to reach that score and stopped playing OR they got bored or frustrated and stopped playing your game.

If this happens to you, you may think about adding more depth by implementing an EASY and an HARD level stream, so every player finds the right difficulty to get used to the game and built up their skills in mastering it.

As a developer, because you play your game all the time you will lose the feeling for being a beginner in your game. On the other side you will merely not try to beat the game as a whole because, you are testing it all the time and got bored of it.

So it is essential to get some neutral mechanisms inside the game were you can watch how the world is doing with your game.

I would be very interested in how other developers approaches that specific topic inside their games and may share their experiences. Just leave a comment!