Letting the CR pass does very little to alter the course of action.

Defeating the CR does even less to alter the current course of action. In fact, it makes it even worse. It further weakens all of the government agencies at a time they're under attack, it muddies which party is responsible for loss of government services or negative economic outcomes, and it gives the Administration vastly larger powers to attack the civil service if the shut down goes beyond 30 days.

Sen. Patty Murray and Speaker Emerita Pelosi (among many others) are neither political naifs nor flame-throwing left-wingers.

Neither are they disinterested apolitical observers. They both have constituencies, they both face political incentives and pressures, and they both have the luxury of being able to cast "no" votes against the CR without having to bear responsibility if the CR actually fails and the government shuts down. It is 100% in the best political interests of those coming from the more progressive part of the party (even if not flame-throwing) to attack Schumer over this....which is why Schumer agreed to take the heat. He knew that the heat would have to come - that all the folks like AOC (and Murray) would have to attack the decision, because their voters are going to be bitterly disappointed.

But it's still smart politics to pass the CR rather than step into the horrible trap of precipitating a government shutdown.