Is Splinter Cell too hard for gamers, or too hard for reviewers?

Splinter Cell ‘too hard to sell’, says Ubisoft’s Jade Raymond:

“One of the things that held it back is despite all of the changes that have happened over the years, it’s still one of the more complex and difficult games to play,” Raymond told Eurogamer.

If the true value of a game is longevity and learning, the ‘instant hit’ needed to sell a game needs to be traded away. I wonder if the real issue is that the game is too hard to play in the first two hours, and most reviewers who post scores that are picked up by Metacritic mark it down in this first few sessions?