So RMT has always been there. Back before they stopped listing them, people were just selling EQ items and accounts on ebay. After that various early plat/character broker sites popped up to fill the void. From very early in EQ's history its been possible to spend money to get stuff in game, including accounts with lots of hard-to-acquire items. For that reason I can't say that "illicit" RMT has really been a culprit in what's become of the MMO genre, since it's basically always been a factor.
On the current crop of EQ TLPs krono farmers have a big presence in the "mindshare", but I'm honestly not sure if it's just that we know what they're doing/notice them more, or if there really are more krono farmers than in the past. I'd say there are probably roughly the same (percentage-wise) in terms of the "professional" krono farmers, they're just more visible now. I remember ages ago on my original server you'd see weird dudes who were clearly playing 3-4 accounts and would camp stuff a lot, as far back as classic. At the time I didn't really "get it", but through the backward lens and more experience I realize these were dudes making money off of EQ, I just didn't recognize it for what it was at the time.
I do think there are probably more "casual" RMTers in modern EQ TLP because it's gotten so easy to unload stuff since you can just generate in-game krono and quickly sell them for cash. I know a lot of people who I wouldn't classify as "krono farmers" who sort of casually acquire kronos and cash them out periodically on redguides or playerauctions.
Cash shops I think haven't really fucked up WoW or GW2 because in those games it's basically either purely cosmetic stuff, or trading USD for in game currency. But in both games the "power boosts" you can acquire for your character solely through in-game currency are pretty limited. They're there, but they're limited.
EQ I think initially was similar, most of the cash shop stuff was cosmetic/appearance based, but it's slowly gotten worse and worse and now it's bordering on true "pay to win." Some examples would be:
-Store mounts that move very fast (used to be bought mounts gave you a cosmetic appearance, but you couldn't get the faster speeds just by paying $)
-Store mounts / familiars / illusions that give decent in-game buffs, that you have to work pretty hard to get comparable familiars/mounts in game.
-The run speed / levitation / buff potions kind of are like obvious pay to win. Most of them are just analogues of player-granted buffs but they're 4 hours and persist through death. They're a way to not need a druid for SoW or a enc for mana regen and it's hard not to view them as getting an in-game advantage with real life $.
-The whole All-Access / Free membership scheme is basically pay to win. I don't actually mind this one, because I don't buy into the idea that an MMO should be free. But it is kind of obvious what goes on here, free members can't use Prestige gear, can't have more than like 1000 AA, can't use AA Auto-Grant, can't get almost any of the Loyalist Rewards from the Loyalty Token vendor, can only use A5 mercs (which are way worse than J1 Mercs) etc. This one bothers me a little less if you view free membership as a "preview mode" and All Access just giving you "full mode" of the game.
-EXP potions are another big play to win, you basically can't competitively level without running the max store xp potion your entire level grind, so people willing to spend cash are getting a huge advantage.
FWIW I've probably spent over $1,000 on EQ in Daybreak cash, 40-slot bags, EQ expansions to get more 40-slot bags/in-game buffs (EoK teleporter stone, rhino mount etc) in the past few months. This money has given me significant in-game advantages.
