Well, Zelda has never been exceedingly deep or difficult for the most part. It's pretty much as introductory level as you can get, being the game that inspires more difficult versions of the same basic gameplay style.
I can however see where he's coming from though to an extent, we have more gamers now than ever before since gaming has become considerably more mainstream. The lowest common human denominator has always been very low... the typical person... rather pathetic when you start looking at averages.
When you look at the number of people buying shooters, or things like "Farmville", and how base such things are... well it's understandable for people in business to want to grab some of that cash for themselves rather than continueing to cater to a niche market. The differance between a good profit, and a monster profit.
Plus I'll be a bit honest, to some extent I can see where he's coming from. Zelda always struck me as being pretty kiddy-kiddy at it's roots. It however grew up with it's fan base and has been morphing and growing darker with time, losing a lot of the elements of what made it Zelda. "Twilight Princess" is about as dark and "Grown up" as you can get without really decimating the charm of the franchise. What's next? Have link trade his green for leather bondage straps, his wavy locks and cap for a punk haircut, and have three out of his four limbs severed in grotesque torture (which he must avenge) only to be replaced by master swords.... his remaining hand used to carry the shield, as he runs around like a "Silent Hill Monster" (click, click, click) flipping through the air like human shuriken....
I don't much care for simplifying it, but really I don't think this was a franchise intended to push the evelope for jaded people in their mid 30s. Those of us in that age catagory will of course still doubtlessly play it, but I think while the general depth should stay the same, a general return to it's innocent roots would be a good thing after "Twilight Princess" and "Majora's Mask" (the former having perhaps one of the most powerful stories in gaming, even if it's not one of the deepest).
http://www.youtube.com/watch?v=GgMOFpvEXNY