If you tallied up all of Starmer's initial decisions, I think he got a lot more right than wrong (not saying there havent been bad ones, mind). What he hasn't been able to do is convince enough of his party on the more difficult-to-swallow ones.
That is a shortcoming on his part though, given his hefty majority.
Others that he did push through, like means testing the winter fuel allowance, he u-turned on because of how unpopular they were, and how unpopular he has been. If he had more political capital, he could have held steady.
I feel a bit badly for him, tbh. He's been good on international affairs, and would probably have done just fine as PM in less economically challenging times. It's a charisma thing - you need bags of it, and the ability to lay out a confident vision for the future - in tougher times.
He's undeserving of the hate he's received, but does not tick all the boxes needed for the current moment.