> Heck, even the "royal door of XXX king palace" is a 1-meter wooden door with carvings that aren't particularly fine

Perhaps your subjective standards are not universal when determining cultural/aesthetic significance of artifacts.

I saw a railroad spike in an American museum once, it wasn't decorative, or made of precious metal (just steel), but it meant something to the locals. I don't doubt the other adjacent pegs were scrapped or rusted away, but that peg was culturally significant due to the historical nature of the railroad itself.