I know Mearls has played other games (or has at least heard of them), so why is he still insisting that one of his reasons for eliminating most meaningful decisions is for the sake of making character generation quick?
First, what about all the other levels? In most cases you get to make one choice at 3rd-level that locks in the rest of your decisions down the road. Second, there are games where you get to choose something at every level (or whatever amounts to a character milestone), and character generation is not only quick, but actually quicker than 5th Edition.
In other words it is not like allowing players to make decisions throughout the course of the game slows it down in a noticeable way. 4th Edition allowed you to make several meaningful decisions at 1st-level, and it was incredibly easy to come in under his arbitrary 30 minute benchmark (yes, even without Character Builder). I would also argue that it does not dilute the "feel" of Dungeons & Dragons, unless that feel for you is writing down what the game tells you most of the time.
He further tries to justify this decision because the first two levels will normally take about a session each, and that if you want more stuff that you can always start at 3rd-level. The problem is not that players like me want more options at the start, but that we want to make more decisions. Not necessarily as many as what 4th Edition provided, but there is a decently-sized middle ground between choosing a suite of four or more powers, and just writing down whatever the designers believe defines an archetype.
But maybe for some reason you actually want to extend the play time of those first two levels. I have no idea why you would want to...I guess some people might have a hard time committing that one class feature that every other player with the same class is also using to memory. The good news is that there will be an optional experience progression to help pad it out.
Okaaay, but why not do something actually interesting with experience points like, say, provide a more modernized system, even as an option? So instead of killing monsters to accrue ultimately pointless heaps of points, players have the opportunity to collect a handful each session, and only need a few to level up. You could also spend them on incremental advancements. I get that big numbers is what was done before, and having tens, maybe even hundreds of thousands of experience points looks impressive insofar as large numbers can, but it is still unnecessary.
He claims that by "allowing" players to choose what level to start at (which you always could), and an experience point system that allows you to drag out various parts of the game will somehow allow you to run a campaign the way you want. It will not. Sure, it lets me control the speed at which the players can make their cookie-cutter characters kind of dissimilar (well, assuming no one else picks the same subclass), but there are a number of other factors like fragile characters, a reliance on magical healing, and pseudo-Vancian magic that not only prevent me from running the game the way I want to, but also do not have much precedence in fiction.
He wraps things up with the statement that "flexibility has always been a hallmark of D&D". No, no it has not. If anything prior to 4th Edition one of the "hallmarks" of Dungeons & Dragons was needlessly monolithic classes: you pick a class, check the level, and write down what it says you can do. 4th Edition broke from that tradition by not only having you decide most of what your character can do at the start, but allowing you to make another choice at every level. 5th Edition undoes almost all of that, stripping out most of the choices and doing most of the work for you. That is opposite of flexibility.
The only upside is that, for now anyway, you will be able to choose your own skill and tool proficiencies. Given all the confusing mechanical rollbacks I find it a refreshing-yet-strange deviation from 5th Edition's charted course, I just kind of assumed that they would go back to 2nd Edition's model.
Speaking of model, I am not sure what "old model of limiting skills by class" Mearls is referring to. 4th Edition kind of limited you, except that anyone could take a background to have access to a skill or spend one of numerous feats to become reasonably competent in any skill (or even go with a Multiclass feat to get a skill and something extra), and even 3rd Edition let you spend skill points on almost any skill you wanted (though cross-classing usually sucked).