My boys would tell you that I used that trite expression throughout their childhood: it’s not what you say, it’s how you say it.
Constructive criticism is valuable, but some people are cruelly critical. I think many are miserable and they want company, so they spread their toxicity. I suppose they’d say it was how they were raised but that is lousy justification for desirable behavior, never mind poor behavior. I emulated some of my parents’ practices and mindfully discarded others. Sometimes, I catch myself doing something that they did, that is not helpful, so I work to change it.
I am not saying to be saccharin sweet. Neither am I saying to lie. What I am suggesting is honesty without cruelty. It has nothing to do with the person being told and everything to do with the one speaking. There are techniques to help if this is a totally foreign concept and one does not know where to begin. “I” statements, for example. “I am frustrated because you leave your dirty dishes in the sink” instead of “You are a pig”. The first statement expresses a fact and the second one is not only hurtful but also not helpful.
You don’t need a script. Just play nice.