Good discussion of your position. My $0.02US...
That is definitely a benefit of 5e’s design. For me personally, high-level barbarians being fast and easy to make is not a worthwhile tradeoff for barbarians of all levels being boring to play. But that’s just my personal taste, and I’ll grant that thee are definite benefits and drawbacks of less mechanically complex design.
I'm not sure I agree that 3/4e had classes that were all fun to play -- instead, what you had was a bunch of barbarian concepts that were pretty boring/bog-standard, and a few who were insanely fun for the right kind of player because they broke the game. Same with every other class, only the ratio of bog-standard to broken builds changes by class.
No, it’s not. It’s clearly explained why they decided to move away from trying to “fix” poor DM and player behavior with rules and design for flexibility over consistency of play. It’s also explained that the design for consistency of play was at odds with designing for a heavy emphasis on mechanical options. But you only have to change one of those two design goals to resolve that conflict. They instead changed both, and I would have preferred they only change one.
Except if they only change one, they don't really commit to their design goal, because both changes support it. Specifically, both changes reduce the amount of complexity in the game, which would otherwise focus player and DM attention on the mechanics of the game rather than the other elements that make the game, as an RPG, distinct from other kinds of tabletop games. I mean, I was a fan of 4E, but I know a lot of people who basically got bored with low-level 4E play not because it was a bad system, but because it was pretty much the same game mechanically they'd just played a couple of nights before when they played Arkham Horror or Touch of Evil or Last Night on Earth.
If you try to reduce the rules overhead, but leave in the high amount of mechanical complexity, then what you have is a game that tries to pull you in two different directions -- do you focus on the simplicity and free-wheeling aspect of the game, or do you dive into the mechanical complexity and ultimately find the unbalancing factors there (which become unbalancing much more rapidly given that the rest of the game system isn't trying to hold those factors in check anymore). Ultimately, the mechanical complexity will 'win' in most games, because, as noted many times previously, optimization as a play style drives out other play styles.
The designers had to do both, or they had to admit that their stated design goal wasn't their real design goal.
His words, not mine. Kindly leave the pedantry aside and engage with my point, which is that mechanical options can be designed to support narrative identiy.(sic)
But why? There are already literally countless ways your 1st level rogue can be different from my 1st level rogue. Mine could be a street urchin while yours is a bored noblewoman looking for excitement. Mine could be looking for a big money score while yours sees wealth as people or organizations rather than money. Mine could have a flaw where he claims not to want to be a hero, but can't help throwing his hat in when needed, even if there's no money in it, while yours can be as brittle as a dry bone when presented with unpleasant choices. The ways to distinguish your rogue from mine are unlimited within the context of a role-playing game; that both characters get Sneak Attack at first level doesn't invalidate this, and arguably having a rogue option that got some ability other than Sneak Attack that you could take at first level wouldn't necessarily make our rogues any more distinguishable as characters, just as game pieces.
First of all, I don’t consider power gaming an inherently bad thing. It’s certainly not at odds with roleplaying. Players can do one, the other, both, or neither, there is no conflict between them.
I fundamentally disagree. Rather than spend yet another post trying to explain this, I'll just point you at a very well-written essay
(from back before 4e even came out) that makes the salient point:
"The 'character' must make choices based on personal motivations rather than strategic or tactical advantage. This is the 'My Character Wouldn't Do That' factor. The correct move in chess may be Queen's Pawn to Pawn 4, but if the King decides, 'I want to protect my Queen more than I want to protect my Bishop, even though the smart move is to protect my Bishop,' then we have a roleplaying game."
More importantly, the ability to break the power curve stops being a problem when the design philosophy is to empower the DM to make decisions based on the needs of their table, rather than designing to make the rules as consistent as possible.
No, it doesn't. What it does is means that the DM now must serve the role of maintaining balance that previously was presumed to be the designer's role -- in that sense, had the designers gone this route, I'd agree that you could call them 'lazy' for making up a game with a ton of mechanical complexity and then, when DMs asked for help balancing the options, just shrugging their shoulders and saying, 'nope, that's your problem."
My point is, Mearls clearly illuminated a conflict between two parts of their previous design philosophy. They changed both parts instead of just one, and I would have preferred they just change the one.
You're missing the bigger picture -- both parts of the philosophy implicated the same goal, reducing mechanical complexity and rules overhead in order to get the game closer to a goal of supporting different styles of play.
And while I don't necessarily think you're a bad person just because you're a fan of power gaming, I will point out that Mearls himself starts the thread by effectively saying the lesson of 3/4e is basically, 'if you design a game for jerks, expect to have to deal with jerks'. I'm involved in an infrequent Pathfinder game, and my feeling at the end of each session is always that the biggest problem with Pathfinder as an RPG system are the people who really like Pathfinder as an RPG system.
For all the flack 4e got for “every class feeling the same,” I see that issue much more with 5e.
My guess is that all of your 5e characters feel the same because they are all the same: the "my character is the best in the world at what he/she/it does" character. I find it curious to consider playing endless variations of the same character as a role-playing game, just as I'd find it curious to see someone lauded as a 'great actor' when he only ever portrays one role. Adding more mechanical complexity wouldn't actually make a better game; it would just allow you to distract yourself for a bit longer before realizing you're just playing the same character, over and over, in a glorified board game.
If that's what you want to do, cool -- as noted by other posters, there's a ton of third-party material to let you do just that. Just don't cram it into the 'core game' where I as a DM have to deal with it, because running a game where I'm dealing with the characters' mechanical strengths and flaws is way less interesting to me than one where I'm dealing with their personality strengths and flaws.