I don't know if you've ever played WoW, but each class has abilities and they have cool downs. i.e. Once used, a certain period of time has to pass before you can use that ability again. In WoW, you have some abilities you can use any time, you have others that have a longer cool down period meaning you could only use them a limited number of times in an encounter, and still others that might have a cooldown period lasting 10 minutes or more. Within a few hours of playing WoW, I made the connection to how WotC structure their abilities to be used at-will, per-encounter, or daily.
When 4e came out, most of my friend group who played d&d was already on WoW. And yes, our first impression was - damn, this feels very similar. Basic attack - at wills, short cool down - encounter, long cool down - daily (basically, ability for boss fights of the day).
Then you have the player character role which was DPS, Tank, and Healer. Your DPS existed to deal as much damage as possible in as short a period as possible to the enemy. The Tank existed to get punched in the face by the enemies so the DPS and Healer remained untouched. This corresponds to the Striker, Defender, and Leader roles in D&D. In WoW, the duties of crowd control were generally spread out among several classes, so there was no single Controller role in a group.
To be fair, roles, albeit more informal, were part of d&d long before WoW came out. We had our tanks, healers and damage dealers before. Fighter was tank, cleric was healer, wizards were damage/control, rogues were skill monkeys. It wasn't unusual to ask what are other people playing ( healers were not very popular choice ) before creating characters, so we would cover all basic roles. 4e was just first edition to give classes official role classifications.
It's obvious to me the design of D&D 4th edition was influenced greatly by MMORPGs. I'm certainly not arguing 4th edition was an MMORPG nor am I arguing the influence was negative. My theory is WotC was a bit nervous about losing players to MMORPGS. I know there was a period of time when my gaming groups were lamenting the loss of players to games like Dark Age of Camelot. You don't have to agree that 4th edition was influenced by MMORPGs, but hopefully you can see the logic behind why many people see the connection.
WoTC sucessfully identified primary competition. Problem is, they went in wrong direction. They tried to compete with mmos in things that mmos do exceptionally well, instead of focusing on things that ttrpgs do well and mmos have hard time emulating. Tactical combat, with situational bonuses and penalties, conditions, positioning etc, computers do that recalculations in milliseconds. At table, that takes time and energy. TTRPGs excel in narrative flexibility and player agency ( in mmos, if it isn't coded in, you cant do it) regarding interaction with game world.
Honestly, this opinion is so widespread and culturally dominant that sometimes I wonder if me holding the opposite opinion isn't just some kind of kneejerk hipster BS. Is there anyone else who thinks Classic, 2e, and 4e are better than 1e, 3.5, and 5e?
2e, specially late 2e with player options, skills and powers and other splatbooks is better than 1e. 4e is, from pure design standpoint, best designed edition out of all of them. It has focus on singular play style and robust mechanics that support that play style in great manner. If you want a deep, balanced, tactical wargame with RPG elements, no other edition provides that specific support as well as 4e does. Honestly, i think biggest problem with 4th ed is that it came out too early. If 4th and 5th switched places, that would make way more sense. And i say that as someone who doesn't actually like 4e.