As others have said - is a tidy room even a battle worth having? How much mess would you tolerate?
DD is a teen now, but at that age we did find that getting rid of a lot of younger age toys to the charity shop really helped. Otherwise she would get all her old stuff out, but she was not really interested in playing with it anymore, and would just get bored and leave it, and get more out, and repeat...🙄
Our rules have always been - no food in her room, drinks ok but cups bought down, dirty washing in the wash, and floor cleared when I want to hoover.
If she hears me hoovering, and her floor is still not clear when I go to hoover upstairs, I just leave her the hoover and she has to do all the upstairs rooms and landing. This has been a great tactic as she hates hoovering (to be fair, the hoover is an absolute cunt). If she is out, I just chuck everything else onto her bed and carry on. She can sort it out at bedtime, or chuck it back on the floor. I may also, to her absolute horror, open the window to let fresh air in 😱
Generally, our attitude is that's it's her room, she can live in a pit of dispair if she wants to, as long as it doesn't encroach on the rest of the household (e.g. smell, leave us without enough mugs/teaspoons, or cause us any significant extra cleaning effort).
Yes, we do still sometimes have these rules broken. I find the odd choc wrapper, or yesterday's coffee cup, or some socks on the floor, and she is arty so there is always a massive pile of pens, paper, drawings and crafting stuff all over her desk that occasionally overflows. It rarely gets to the point where it is a problem.
I don't expect spotless, I do expect it not to be minging.