Experience is certainly a factor when something you have only performed once, or never had to deal with, happens. You may be just fine when everything is routine, but if an emergency that you are not prepared for occurs, and you are alone and do not act quickly enough or act correctly or maybe do not have that bag of tricks to apply and try, or you panic, or you don't know what to do when the one thing you did try did not work, or you are not able to sort things out quickly enough and remain calm, these circumstances or a combo of them may be an issue for a very young pilot with very few hours under their belt. THAT is what I am saying.
We seem to be focusing on maturity solely (which can be an issue, depending on the individual) and completely letting experience as a possible issue fall by the wayside and be disregarded for some reason. If you are the most mature person on the planet, but lacking enough experience, confidence, focus, the ability to control your emotions and not panic, along with the other factors I have mentioned, in certain situations, these aspects can and will be a factor. That is all I am trying to point out.