Bolding mine. In that bold is the basic problem.
Players have goals. Designers have goals. Mechanical advantages do not - in the same way that a hammer does not have a *goal* of hammering nails. Chunks of steel on sticks do not have will or desire, and have no goals. The hammer can be used to tear down drywall, if that is my goal, no matter that the designer of the hammer had a goal of making a thing to hammer nails.
The designer cannot set the player's goals. The designer can only choose designs that support particular goals more, or support them less.
Having lots of strong mechanical choices supports power gaming, whether you want it to or not. All players have to do is take on the power, and not role play the matching narrative identity - it is the old "role playing restrictions are not a reliable way to balance mechanical strength" issues of Paladins in 3e. And, having supported power gaming, then you are back in the 3e/4e power-curve-breaking mode, because having supported it, it becomes a major way to get rewards as a player.
I like this. I think Mearls is thinking more in favor of how can D&D be better for the DM with 5e than the more Player facing 3e and 4e because both 3e and 4e do provide a lot more mechanical emphasis and options for Players, which probably did make those games more difficult to DM for.
At least on the surface it seems that way. But Mearls is making a lot of personal biases creep in and putting his own beliefs into what D&D is supposed to be, and its definitely in favor of making the game appear to be more narrative focused by how the game presents information, the game's mechanisms, and the whole paradigm of De_emphasizing "Rules" in favor of "Rulings" for different DMs to manage the game as they want.
All this is why I personally dislike 5e. As a Player I don't like how so many of my decisions are allowed by the DMs personal perspective on their Rulings and because I don't have Rules to fall back on, this leads me to feel quite often that my personal Narrative Identity only matters if the DM chooses to allow it.
Plus, 5e has no game mechanisms to really support Narrative Identity. The way its written it presents a very good illusion of it, but if you read carefully, most of the actual rules are phrased like "When you do an Action you MAY DO... (Insert possible action)."
There are no concrete rules in 5e for Players to fall back on. 5e provides no Player Agency, as the game is entirely based on how the DM decides to make their Rulings.
As an autistic person, I love this as a DM and I hate it as a Player. All of this is why I love 4e a lot more as a Player. Because in 4e, I can look at my character sheet, see my abilities, and I don't need to ask the DM if I can do something because my abilities gave Me as Player the ability to make real mechanical decisions and See the Results.
This in turn would cause a 4e DM to have to be more adaptable, and be able to make decisions based on what the Players chose to do.
And yet 4e did provide the DMs full ability to make rulings on everything else not codified by all the rules, just see page 42 in the DMG1. That one page provided a sure fire system to enable DM to come up with a great way of handling more Narrative Agency in the more Narrative focused scenes.
The problem was that so many people only saw the presentation of the rules that they never really delved further into the actual design mechanisms of the game. And this makes many of Mearls' suppositions of 4e incorrect.
As designed, if you really read the 4e DMG books, they provide the DM an incredible amount of flexibility and narrative tools to adapt and create many narrative opportunities. Way more than 5e's design, which is pretty wishy washy and up do the whims of the DMs own personal biases that can often take away from the Players actual agency to make real narrative decisions. The fact that the 5e DMG can talk about Inspiration for many paragraphs and yet does not provide a real single mechanical system for handing Inspiration out is proof of this.
But I am a player who see's rules as narrative support and provides players with more agency and 5e's approach as taking away the players agency to make any kind of real decision making since every action the players can do begins by asking the DM if they can do it.
