Consultancies are not doing that.
I’m not sure why certain businesses should be “banned” because YOU believe they do not add value. Do you pay them? No.
It’s not correct that they are proxies for decision making that mangers don’t want to be responsible for. Neither McK nor BCG could run at the scale they do for five decades if that was the case.
But I suppose that was just your happy Sunday rant of the day to let off some steam.