That's not how structured debates (Policy, Public Forum, Lincoln-Douglas, etc) work. Judges don't tell a team their facts are wrong, the other team does. Judges decide which of the teams had better argumentation. If you spout lies and I don't call you on it, as the opposing team, I will probably lose.
But let's say we accept that this is barely a structured debate, and the structure that was there sucked anyways, so hey- maybe it's was really a speech event (like Big Question, Extemporaneous, Humorous Interpretation, etc). That makes it even clearer why people are reacting like this, because those are not about facts at all, they're all about performance (as in 'acting').
My own view is that presidential debates are more akin to throwing the candidates in a gladiatorial arena and seeing whoever comes out least bloody. And that was always going to be Trump. Biden and his team are to blame for this, because it never should have taken place.