do you disagree that 4E has more "video game-like" elements than 5E? That hardly seems like a controversial statement, especially considering that 5E was clearly an attempt to hearken back to a more traditional game.
Well, the only video-game-like element that Mearls identifies is "pew pew" magic, which is in both.
I don't play video games, but I have friends, including RPG friends, who do. When I think of the elements that are characteristic of video games I think of images on screens, inputting commands via a keyboard, and the absence of meaningful fiction (there is flavour text, and there are superficial tropes, but no genuine theme or plot). In both 4e and 5e representation is primarily by way of the spoken word (ie no screens), input is primarily via the spoken word and resolution is either free-form RP or via manually executed maths (ie no keyboard inputs to a computer), and at least in my 4e experiences meaningful fiction is the order of the day.
The terminology of strikers, controllers, marking, etc. was absolutely baffling to my players. Not only were the terms alien, but we had never thought of classes in terms of their tactical role (we never used a grid). Wizards use magic. Fighters fight things. Thieves sneak around and steal things.
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I can't speak for people coming to 4E from MMOs, but a group of players coming to the game (even the more traditional Essentials version) with 30 years experience found it a jarring transition.
As someone who has never played a MMO, and who never used a grid or tokens as part of combat resolution prior to playing 4e, I can report that I didn't find the terminology baffling, nor the "transition" jarring.
In all the fantasy RPGs I've played, wizards also fight things (using spells like magic missile, fireball, etc) and thieves also fight things (by ambushing/backstabbing, and also as light skirmishers). So fighters aren't distinctive in their propensity to fight. And it was clear to me that a striker was a skirmisher (a bit like the classic D&D fighter/thief, kensai or warrior monk), a leader was a healer/buffer (the classic D&D cleric), a defender was a front-line combatant (one version of the classic D&D fighter, paladin or fighter/cleric) and a controller was a classic D&D wizard (using AoEs and conjurations).
These different character types were all familiar to me from playing D&D and other fantasy RPGs for a couple of decades, and certainly don't depend for their definition on the use of a grid.
Maybe this was because I've played and GMed a lot of Rolemaster, and so was more familiar than some D&D players with the idea that a single wizard can't be good at everything but has to focus somewhat, and also with the difference between skirmishing warrriors and front-line warriors (RM's movement, armour and ambush rules make this distinction more important than it is in AD&D). But that has nothing to do with MMOs: Rolemaster reached its 25th birthday as an RPG before the release of 4e.
4e openly embraced the MMO idiom. That is, they said, "Video game players are used to this kind of approach into the game (tanking defenders, healing leaders, crowd controllers, mobile strikers, cool down periods, monster PCs, etc.), so if we make these characteristics -- long part of the game -- more salient, it will be a smooth transition for them to get into the game."
That's probably right - because I'm not an MMO player, I can't really tell except via the reports of those who are.
What I can say is that having the designers state what they think a class is good for - and, as a corollary, trying to ensure that no class was good at everything - didn't seem to me to do any harm. And from the get-go I've never experienced roles as "straitjackets".
The sorcerer in my game is a damage dealer who also controls (mostly via forced movement) and does the occasional party-wide buff (bard multi-class).
The fighter is a martial controller (lots of close bursts and polearm stuff) which means that he also deals quite a bit of damage (but spread over multiple targets).
The ranger is mostly a "pew-pew" archer but has important debuff capability (Disruptive Strike) and is also a hybrid cleric for healing and a bit of AoE.
The wizard/invoker is the party "skill monkey" and ritualist, who in combat does very modest damage, facilitates party mobility (teleports, invoker slides, etc) and has a few big control/debuff abilities (blinding, domination).
The paladin is tough, helps out with healing and a bit of buffing and debuffing, and engages single foes with quite good damage, especially vs bloodied targets. He's probably the least focused PC overall.