Having never played WOW means than you have no chance at noticing any similarities at all.
That strikes me as incredibly dubious. Especially given that, as you quoted, I
do notice similarities. In all editions of D&D.
4E continued this and dispensed with any remaining mystery by listing items as actual gear in the PHB. Another 4E addition to the magic item situation is the ability to disenchant unwanted magic items into residum.
This is a direct WOW import as items in WOW are routinely disenchanted into materials that fuel item enchantments.
This concept was in games and fantasy fiction well before the existence of WoW. That I know. And yes, I knew that this was in WoW as well, even without having played it. So while it is a similarity with WoW that did not exist before, I still don't see evidence that it was actually a "direct WOW import".
Aggro mechanics: There have been tank, glass cannon "striker" , and healbot archetypes long before any MMO. The computer games simply used the archetypes that were already in use on the tabletop. Not having a live DM meant giving the AI mobs a reason to attack the toughest target even if that would be a far from intelligent choice. It allowed players to use teamwork to "tank and spank" a monster. This is a game mechanic that is not needed for a tabletop game. This goes back to the oldest rules of game design: The rules serve the game and not the other way around. Aggro based mechanics are good example of a game serving the rules. The rules say something works despite any logic or reason so either the game changes or the world simply obeys the rule without question.
This is an MMOism? People have been complaining about things happening in D&D without (sufficient for the individual in question) logic or reason for as long as I can remember. I
was one of these people, a good 10+ years before MMOs were invented.
Retraining: 3E had this before 4E and its a common occurence in WOW. Some WOW players "respec" or retrain daily depending on if they are grouping or playing solo. This has the benefit of letting players tinker with different bits of the rules but the constant overwriting of skills and abilities makes a chartacter feel more like an avatar or toon than a part of an ongoing living fantasy world. The concept of "bad" decisions being judged so because they were not optimized for job X even though the player had fun with that choice is one that seems more at home in tabletop battle games than in a roleplaying game.
That this is similar to WoW I can't deny, but since, as I said above, every edition of D&D is similar to WoW, I'd like to know why people think it
necessarily came from WoW instead of simply being a clever mechanic that happens to show up in more than one game.
I've never had a "cartoon"-feeling when using the retraining rules, or even letting people "retrain" feats and stuff before the rules for such in 3E ever came out. This might be just because I used them with some restraint. When my 3E Dwarf Wizard retrained his Toughness feat for something else, he didn't lose any hit points, because retraining only happens on level-up. He just gained fewer hit points than he would have at other levels and ended up with one more other feat.
Likewise, if I retrain my skill training in a typical 4E game, it's usually because I just haven't been using the one skill and think I'd like to gain another. So there's no disconnect where my character used to be spouting off random Nature facts and suddenly can't tell poison ivy from crab-grass - if the skill was being used all the time, I'd hardly have reason to retrain out of it. And since I can still only retrain on level up, you notice me learning the new skill around the same time everyone is learning new things. So you might notice that I learned more than someone else, but that happens to people in real life all the time and doesn't seem like it should be immersion-breaking.
When a wizard realized he learned a spell that turns out to be less good than he hoped, he may decide to seek out another one. And even though he probably still is casting his crappy spell all the time, when he learns that substitute spell (read: levels up, retrains) why would he go back to preparing that crappy spell in the slot instead? If it's not one of his "slotted" spells, why would he use that crappy spell in place of one of his other at-wills or encounters? It makes a reasonable amount of sense that the unused one will atrophy.
I can totally understand that it
can be done in radically immersion-breaking ways, and that someone reading the book can go "that's ridiculous! People can do that in totally immersion-breaking ways! It needs to be saddled with some justification so that people can't break the immersion!" But I've found in play that generally, people don't try to break immersion, and asking them politely not to when they do works. YMMV of course.
There are major flavor changes that align 4E (and parts of 3E) with MMO style games. The largest overall flavor change that may be causing the most resistance is that of genre tone.
4E is not an MMO of course. It is a superhero tabletop roleplaying game wherein the protagonists dress in robes and armor rather than capes and tights. The move from swords and sorcery to supers is I think, the cause of a great deal of the resistance. It would be like taking the marvel supers RPG and turning the heroes into fighters, mages, clerics, and rogues in feel, and leaving them in the trappings of capes and spandex.
I'm not sure how to respond to this other than that I really don't see it (yet). I haven't played a lot of 4E (yet) so some of this might start to ring true. But it doesn't look to me terribly different from BO9S stuff, which I adore, so I doubt it.