I frequently change my mind, which is proof that one or more people out there are changing at least one person's mind. And here's the thing: in nearly all cases, the person or, more often, the people who change my mind never know it. I am often stubborn in the moment and unwilling to admit I've been swayed. More often, I don't realize that I have been swayed until I revisit the conversation over the next months, while adding in new information from other conversations or things I'm reading with a developing perspective. Sometimes my mind changes so slowly that I don't even notice it did until someone quotes back to me the now (obviously! objectively!) wrong thing I used to think.
My point is this: you may be changing minds without knowing it. And another point: even if you aren't, you are likely benefitting personally from having meaningful conversations with people.