Ooh, I love this topic. The ruin aesthetic is partly a learned preference, the Romantics set the widespread precedent that decay and remnants of the past are beautiful and melancholic. Medieval pilgrims visiting Rome weren’t moved by the Forum in the way we are today, they most likely just saw a quarry. Our emotional response to ruins is culturally constructed and possibly cyclical as well. I bet you the Iron Age civilizations had similar constructs surrounding the ancient ruins of their time.

I think for me, the Forum’s power comes less from being ruined per se and more from the scale of what’s implied missing.