Why? It's not a criticism of policy, it's a criticism of dishonest behaviour.
Both her and Starmer were absolutely clear that due to an impending productivity downgrade there was money to be saved or accrued via tax. She knew this downgrade wasn't as severe as previously thought but took the same remedial actions anyway. Where you support tax rises to fund welfare rises is irrelevant in the complains people have against what she's done. It was at best dishonest, and at worst manipulating bond markets to make her budget work.
It's not just mud slinging, it's pointing out dishonestly in office. I voted for these idiots and it was a decision almost as hideous as Corbyn/Boris. We called out the Tories for having their hand in the till, and we need to call out the current government when they make mistakes, not just continue to gaslight the country.