It was an admission of reality. I hadn't heard of a Stalinist that opposed the idea, though I sort of remembered something from a while back that I found.
In one of Lenin's last works he tells everyone to trust Trotsky's interpretation of the NEP:
Lenin wrote:Those to whom the question of our New Economic Policy—the only correct policy—is not quite clear, I would refer to the speeches of Comrade Trotsky and my own speech at the Fourth Congress of the Communist International devoted to this question.
Anyway, the almost religious devotion to a personality is dangerous and tends to be counter-productive. The NEP is a kind of proof of that in that Lenin and the others had to look at economic reality, not what they wanted but what it was, and then apply that to their system.
The NEP wasn't particularly popular, and nobody but Lenin could have pushed it through, but the Soviets were in danger of failing.
The precondition was that the working class retained control over the free trade and whatnot. How much this happened after Lenin is up to debate, as was how this was dealt with and should have been dealt with.
Regardless, few communists would say the NEP was a bad thing.
Alis Volat Propriis; Tiocfaidh ár lá; Proletarier Aller Länder, Vereinigt Euch!