Can I criticize Westboro Baptist Church for their religion if they’re picketing the funeral of a service member who attended a Baptist church, and not the pastor who delivers the sermon? Of course I can. They worship the same god, but don’t practice their religion in the same way. No one is criticizing her for being Catholic; they’re criticizing her for letting her Catholicism determine her decision-making as a judge. Biden’s faith (however fervent or not) is personal, not professional.
I fully recognize that this is a mark against him among evangelicals and conservative Catholics, and that’s all well and good. You do you. Saying you can’t criticize one Catholic and not another when the way they practice their faith is wildly different is silly.