Unless you do what D3 did (I mean, what they did after they tried to solve RMT by making sure they were the ones doing the RMT) and have no trade at all, there will always be RMT.
I don’t think LE’s system is intended to stop RMT. The main purpose of LE’s trade system is to stop the toxic trade strategies you see in PoE. It’s meant to allow players to use trade as a tool for getting gear, rather than it being an endgame mechanic that many people spend the whole league doing. It’s meant to stop sniping/price fixing.
The fact that it also hinders RMT a little bit is just a bonus.