Guild Wars 2

I think that fire can burn most of things in every place, and with right combustive can weaken and destroy stone walls.

Why burn don’t affects objects?
May be good for condition builds if fire affects trebuchets, gates, walls, wood boxes and turrets.

Then you’d need to differ buildings in their material. I don’t think you can set a stone wall or a metal car on fire.

Builds are just made to be immune to conditions.
Developers don’t like conditions.