I’m not going to play word police but I am going to attempt to change your mind. Dumb used to be the medical terminology to mean the same thing as what you said and it’s not considered a slur or a disparaging insult. And so the word does have more bite and it does have power.

I’m not going to get offended if you keep using it as an insult but using it says more about the emotional maturity of the person who said it than it does about the person being insulted by it.