There are historical inaccuracies and then there are historical inaccuracies. Rome is full of them, but they mostly consist of reasonable compression of events and timelines or are just small mistakes (e.g. Cato wearing a black toga earlier than he should). Or characters might appear older or younger than they should. As long as you keep the general story of what happened right, and the general sketch of a character right, I don't think most people care.
What made the Tudors unwatchable, and what afflicts The Borgias to a lesser degree, is really bad acting and boring storytelling. Also, making historical figures look like pouty modern models.