I have had this happen to me several times. And honestly, running down my previous hairdresser does not make you look better. The last time someone did it to me it was actually her sister who had done my hair because my stylist was not available and recommended her sister to me.
This also sometimes happens when beauty consultants in a department store jump out at you trying to shill their products. Lady you are not going to get anywhere with me by running down the products I currently use and telling me how old my skin looks.
Similar can happen if someone comes to do work in your home.
Admittedly, sometimes people do make mistakes, or are just not good. But every single previous person cannot be awful.