RedLeaf said:
Without doing a league wide comparison of NHL players, I will assume that players under the age of 25, and with a grand total of 7 playoff games on their resumes, are generally considered inexperienced.
Experience is based on time served, not age. They're a young team, yes, but they're not an inexperienced team. They don't have a lot of playoff experience, sure, but, we're not talking about poor play in the playoffs, either, and most of the roster does have more than those 7 games worth of playoff experience.
EDIT: There are only 3 skaters that meet your standards of being 25 or under and have 7 games or less of NHL playoff experience who have been getting meaningful ice time - Kadri, Gardiner and Rielly. Everyone else is either 26 or older, or has more playoff experience.