The biggest problem with the whole 'games are being dumbed-down' debate is that it tends to confuse difficulty with streamlining the interface and level design. Those are completely separate concepts which nevertheless feed back into the overall experience a player has with being 'challenged' by the game, but they're not usually the determining factors in how easy a game is. I've been playing games for about a decade now, and I don't think games have gotten any easier to complete.
An extremely complex interface contributed to Baldur's Gate II being a very challenging game to master, for instance, but I don't think complicating the player's interface to increase difficulty should be considered good design. It's like trying to play tennis with ropes attached to your every limb. Dragon Age II is a much easier game to play because the interface has been refined so it's a lot easier to find the fireball spell when you really need it, but at the same time, they've simplified the interface so much that most items no longer have a distinct portrait, taking much of the flavour out of the world. This doesn't really affect the difficulty, but it nevertheless gets lumped in with complaints that the game has been 'dumbed down'. In my mind it's more a case of lazy design.
As Samus points out, this mindset is primarily due to people having the perception that developers want to target a wider audience and are consequently making the game easier to get more people involved. I don't think that's the case, devs will always want more people to get involved, but publishers want them to get games out much faster than ever before, so they don't have time to put in complex game mechanics. Because of publishers, the dynamic has shifted away from 'huge game with 3-5 year development cycle' to 'game with 1-2 year development cycle with extra DLC'. Publishers love DLC for obvious reasons, but in developing extra DLC the devs can only really offer more scenarios for existing mechanics: they can't really make the game mechanics any more complex.
For those of you wanting something succinct to take away from this: gamers aren't to blame for the changes in design, corporatised publishing companies are.
An extremely complex interface contributed to Baldur's Gate II being a very challenging game to master, for instance, but I don't think complicating the player's interface to increase difficulty should be considered good design. It's like trying to play tennis with ropes attached to your every limb. Dragon Age II is a much easier game to play because the interface has been refined so it's a lot easier to find the fireball spell when you really need it, but at the same time, they've simplified the interface so much that most items no longer have a distinct portrait, taking much of the flavour out of the world. This doesn't really affect the difficulty, but it nevertheless gets lumped in with complaints that the game has been 'dumbed down'. In my mind it's more a case of lazy design.
As Samus points out, this mindset is primarily due to people having the perception that developers want to target a wider audience and are consequently making the game easier to get more people involved. I don't think that's the case, devs will always want more people to get involved, but publishers want them to get games out much faster than ever before, so they don't have time to put in complex game mechanics. Because of publishers, the dynamic has shifted away from 'huge game with 3-5 year development cycle' to 'game with 1-2 year development cycle with extra DLC'. Publishers love DLC for obvious reasons, but in developing extra DLC the devs can only really offer more scenarios for existing mechanics: they can't really make the game mechanics any more complex.
For those of you wanting something succinct to take away from this: gamers aren't to blame for the changes in design, corporatised publishing companies are.