The only way to stop RMT is for Nikita to offer 1st party RMT that undercuts the third party sellers and drives them out of business, which would stop the cashflow to the hackers, and allow anti-cheat to be ahead of the curve.
Problem is, you don't want that, because the symbolic permission of RMT going from illegal to legal will mean that way, way more people will do it, and you'll get hyperinflation.
The only way to stop this hyperfinflation would be to fix the price of literally every commodity in the game. Which would make Tarkov almost a single player game, rather than an MMO where every player is connected to a central world (the market)
RMT is inexorably linked to the existence of a free market within a video game. As long as you can trade commodities for the price that you want, people are going to use this trade with the currency of their choice (real dollars in the real world).
If you take out the free market from Tarkov, it might as well be a single player game, and you don't want that. There was another MMO, long before Tarkov called Runescape. It had a RMT problem that the developers needed to put an end to for legal reasons. They did this by removing the free market economy, and it caused the game to be transformed in a bad a way, permanently. So bad that the version of this game before that update, known as "oldschool" was popular enough to be re-released many years later. In Old School runescape RMT exists and flourishes, and people just cope by not caring.
RMT will always exist in a free market game.
Free markets as an idea are fundamentally broken, because freedom means no rules, and no rules means.. well.. no rules. Tarkov is supposed to be a hardcore game with no rules. Inside Tarkov is the zone. Anarchy, chaos, fighting for your life. Is it any surprise that people will do dubious and shady things?