It depends on the game. An easy mode would definitely destroy a game like Dark Souls. MMO's have suffered from dumbing down and simplifying content to make everything but portions of the games "easy mode" in order to accommodate everyone.
I have no problem with adding easier game modes to games, but the ones that do it against the vision of what the game is supposed to be are definitely ruining the game. A game about a struggle for survival quickly becoming a superhero stroll through the scenery loses the context of its setting.
Bottom line, you can't appreciate the victory without a struggle and the easy-mode "push button, receive reward" sort of instant gratification doesn't build anything memorable outside of the short term satisfaction you get before wanting the next instant reward.