I don't see how that's any different than buying gold or gear in Diablo 3 off the RMAH, and that game didn't suffer because of it.
Are you kidding? It's mentioned by pretty much everybody as one of the top three reasons the game failed. Even so, D3 is not an MMORPG, but it has survived exclusively by being a Blizzard game that a lot of fans waited years and years for. The RMAH is widely regarded as its downfall, and is what kept it from being taken seriously by anybody who is remotely competitive.
Name a widely succesful MMORPG with a long lifespan where it has been possible to mastercard your way to the best gear that can be obtained. There's a reason everybody hates it: it completely destroys a game's integrity and eliminates the reason most people play MMORPGs. The very thing that makes a succesful MMORPG is competitive integrity and incentive to excel. Allowing people to RMT their way to the top means the competitive integrity of the game is literally zero. Who would care about WoW if you could pay Blizzard for a full set of BiS gear? Who would care to work hard and beat the content?
Who would take pride in accomplishing something if there was no way for them to distinguish themselves from those who did it by opening their wallets? Indeed, games are increasingly starting to cater specifically to those who mastercard their way to the top, making this the most rewarding and celebrated way to "play" the game. Not coincidentally, we're also in a time where games have a lifespan of like three months before people can't possibly force themselves to care anymore and move on, hoping the next title is more satisfying. It's sad for gaming that these days it's a matter of "woah, that guy has the really expensive vanity pet" rather than "woah, that guy killed the hardest dragon and got the Holy Avenger +5!"
EQ had competitive integrity. DAoC had competitive integrity. WoW has competitive integrity, though it's starting to crack a little with the introduction of shit like the black market AH that obviously serves as a currency sink for people who RMT. Expect the next WoW expansion to have Blizzard-sanctioned Cash For Gold and even more high end gear on the BMAH, and expect that to be what kills WoW. It'll be their last cash grab before they turn their full focus on whatever Titan turns out to be.
An MMORPG where you can literally pull out your credit card and purchase the best gear in the game will be forgotten three months down the line as nobody will give a single fuck about anything that goes on in said game and will have no qualms moving on after two weeks when they realize that there's no incentive to work hard and no recognition for doing so.
It's a bit different in ARPGs where you play mostly by and for yourself, but the appeal and root of success of the MMORPG genre has always been the look-at-what-I've-got factor. Removing this element alienates every fan of traditional MMORPGs, as seen in GW2 and many other lesser titles that few even really know about because they failed so resoundingly that they didn't even cause a ripple in the dead sea of the MMORPG genre.
The games that survive for a long time, and are still remembered fondly even after they've died naturally of old age, are the games where you couldn't buy success and could be fairly sure that the guy with the awesome axe had actually earned it. Nobody remembers all those shitty games where you leveled to max in a day, discovered that there was no point doing anything since a third of the playerbase just bought the things you'd have to work hard for, and then quit without ever looking back. If Neverwinter really lets you RMT the best gear in the game, it will be another one of those games.
The gaming industry has become like the McDonalds of restaurants: it's strangely lucrative to serve people absolute garbage. Unfortunately, unlike the real world's food industry, every MMORPG is now trying to be McDonalds and there's no way to get a proper meal anywhere. People argue that it must be what the paying customers want if it's what's most profitable for the developers, but one wouldn't try to argue that a Big Mac is good food just because it generates a lot of cash.
