While you're not exactly wrong, I think having it as the opener offsets that to some extent. Sure, the performance wasn’t flawless like the studio version, but imo it was pretty solid, especially in 2008 and 2018 (1999 a bit behind, mostly because it was played too fast). The chaos and energy it unleashed at the start of the show made it so that most people weren’t even focused on how it was being sung until that anthemic chorus kicked in which, honestly, would be one of the best Maiden things to experience live. When it’s placed in the encore, or worse, as the closer, it loses that magic and the weaker performance becomes a lot more noticeable (on top of being actually performed worse).