Yeah: when you debate you never change someones mind, especially DURING the debate. The very first rule of debating is that you try to change the mind of the public reading it, not the debaters.
Now what you learn is mostly to argue your way around your opinion better, not exactly to change it. But why would you: you change your opinion when looking for insight (reading a book), not when looking for a win (debating on an advertisement platform).
Debate for an audience is kind of awful. You have to sacrifice your honesty and ethics to score cheap points that don't actually show you're right but can fool the causal audience. What's the value of that though? You've convinced some strangers of a fact that you don't even know is true yourself. It's just creating fake knowledge pollution.
Now what you learn is mostly to argue your way around your opinion better, not exactly to change it. But why would you: you change your opinion when looking for insight (reading a book), not when looking for a win (debating on an advertisement platform).