I agree with everything you said. If the descriptions mostly add flavor and the roll of the dice determines the result, that’s exactly how DnD should be. It is a role playing game, and role playing is half the fun

Unfortunately, it seems like most DMs punish you for roll playing poorly in conversation. In my experience, if you have high charisma it’s often more successful to just say “I want to convince the person of this thing” and roll than to describe your argument to the DM. That discourages roll playing rather than encourages it.