Multiple difficulty settings are a long-accepted practice among players and the industry, but not every game requires them. Even if you normalize your game towards the average player, you can still cater to the far ends of the skill spectrum.
A great way to maintain a single difficulty mode, yet prevent players from getting stuck, is to offer help once they meet a certain condition. For example, being stuck on a puzzle for 15 minutes triggers a hint, or failing to complete the stage five times in a row gives you a power-up.
Successful (and very explicit) examples of such systems can be found in many Nintendo products. Super Mario 3D World gives you access to a powerful power-up after several deaths, while New Super ...
