The issue many people end up having with the cash shop is (A) Almost none of the items are account-wide which actively discourages characters on other server or promotes repeatedly buying the same item, (B) even though it's not main dev time being put into the mogshop, SQEX is spending resources on this and we've been told that Mogshop sales are the only sales that get put back into the game beyond the initial sales, finally my personal issue (C) You have the mogshop selling consumable items like dye, which promotes repeated purchases.
If B is still the case, then the mogshop will only get worse, as it needs to keep expanding for the game to continue to grow; along with the fact that this year SQEX decided to not give the easter event a mount, but conveniently released an Easter themed mount on the shop, so it's very easy to conflate that the mogshop will actively prevent the in-game acquisition of items as time goes on.
Actually, it does deal with the reason as to why gold sellers are bad for the game. In any game, WoW, XIV, etc.. the people who farmed gold and sold it did not do so with the intent of putting the currency back into the games economy through regular play (bots or players continually farm sections of the game and sell the items to vendors in order to get freshly introduced gold rather than deal with a fickle market). They would continually add additional gold into the system that would not have normally been gathered by normal play.. so when they do sell that gold for whatever sum, they immediately inject tens of thousands of gold into the economy.
With the WoW token system, the gold is already in the economy; To gather that much money as to afford a token, you would have to actively play the market board (either adding new items or relisting items) and the money that is already in the system simply is gathered in one place before being used to purchase the token from a player, who will then use that same gold to purchase more things from that market board.
Now, is the system perfect? No. It never can be. It is as close to a solution as you are going to reasonably get in a game however.