I think a lot of the left actually agrees with this, but are able to deny pretty explicitly anti-populist positions by claiming to represent a hypothetical people who will learn to support the right positions at some unspecified time. Like consider the most populist position Bernie held was healthcare reforms that originated from the democrat establishment. The positions he adopted from left academia however were things the larger dem voting base often did not want, things that needed to be imposed from the top down. It was much the same with Corbyn where he was having to oppose existing populist energy in favor of the hypothetical populism that would exist after extensive social engineering.

This isn’t to say that anything that isn’t populist is inherently wrong, but it does seem like there’s a general state of confusion about what the left actually consist of. People have adopted the messaging of long dead movements that had very different bases of power and mixed it with existing movements that have contradicting aims and methodologies.