Long ago we stopped fighting the battle of "clean up your room". We banned food and drink from the bedrooms and made them bring their washing out to the laundry themselves. I told them, I refuse to risk turning an ankle by stepping on something.
I DO occasionally reach in and drag out what I can reach from the doorway, and every so often they get desperate looking for something and end up tossing stuff into the hallway, from where i remove it, never to be seen again. As clothes come through the laundry which are clearly too worn out or outgrown, they don't get them back.
But since we stopped that battle, it made a HUGE difference in our lives.
If you want to still keep them tidying their rooms, one way to make it easier for them, instead of saying, "Go tidy your room," is to say, "Go pick up and put away, TEN things." I've stood in the doorway to referee, and praised them when ten things have been picked up. I usually also say, "It was only ten things, but what a difference it has made already! I can see a patch of floor over there..."
When I return washing from the laundry, they get it either folded neatly, or on hangers. They are expected to put clean clothes away. As a result, the stuff lying around tends to not get used until it's eventually wrecked or outgrown.
I have in general tried to keep their mess isolated to their rooms but lately the boys have (for various reasons) overflowed. I'm working on that, but in general the kids have had to be responsible for their own spaces. I'm waiting anxiously for difficult child 1 to get married and leave home, and for easy child 2/difficult child 2 & BF2 to move out, so I can begin to remove all their stuff.
OK, the house is messy. But it's workable and we aren't always fighting. easy child, the first to leave home, has her own space and is looking after it. She hasn't been damaged by this policy, she is capable of having a presentable personal space. I'm beginning to notice difficult child 3 being personally organised and getting his toys sorted into different containers.
When they work it out for themselves, when they become their own motivating force, you have finally won - and without a shot being fired.
Marg