No, it can't -- see bellow; there's also no quantitative objective stated or communicated. Hence, it is not controllable, whether it achieved the stated objective or not. What would happen, if it doesn't achieve it? Nothing, because it was not promised clearly enough, just in some vague way.

But it happens to achieve different goal -- for example, even more concentrating the control over general computing into fewer hands.

Would it be rolled back, if it doesn't achieve the stated goal? Of course not; it will achieve the hidden ("it just happened, who could ever know, pinky swear") goal, and that's important. Not the pretend-goals that was used to sell it to the general public.

Now, why it won't achieve the stated goals: because spam is problem also with closed systems. Ever got a junk call? Users use only "approved" devices, and even if the system can put limits on the source, it also limits how the destination can protect itself. The important thing with spam, scams, etc. is, what whenever there is a possibility to make money, the scammers will find a way. Even with low-tech approach (like hire a bunch of human operators of the approved machines). They weren't stopped even when what they did was illegal, why do you think RA achieve what the law didn't? To make things worse, the closed nature made it more difficult for the victims to save evidence of the spam, scam.

So of course it won't reduce the scams. But it will make the situation worse for us all. And web losing to proprietary platforms? It will certainly lose, when it is turned into one of the proprietary platforms.