I hear you OP, children are so messy 😫
I have autoimmune arthritis that makes doing lots of housework painful, so I've had to really work on this with mine in the last year and we do finally have it to a point where he does his bit (with a lot of stress along the way). I appreciate this is probably harder with four, but what worked for me was:
-kids like to feel grown up and important, so it helps (in my experience) to give them 'grown up' jobs- hoovering, cleaning the sinks, mopping (with one of those mops with a changeable pad so the water doesn't go everywhere).
-how you ask makes a difference IMO. I do a lot of 'oh gosh, I'm feeling so tired and I'm worried I can't manage all this tidying/cleaning on my own. Hmm, what a pickle, what on earth will I do????' Sounds absolutely ludicrous but there's normally an eager little person wanting to 'save the day' 😆
-lots of praise when they do something to help out, make a really big deal of it. It helps if they can see the benefit in helping out- 'wow, because you all helped me do xyz, I now have the energy to go to the park' etc etc. My DS loves being told that he's really made a big difference, how pleased I am that he's sensible enough to do xyz.
- for tidying toys/craft stuff/whatever, that is the most boring task that most children hate (from my experience as a primary teacher). My trick is to say I've chosen a magic object- it's a secret, whoever finds it and PUTS IT BACK WHERE IT BELONGS is the winner. Cue frantic tidying. Once it's been found and put away, pick a new secret object, rinse and repeat until the room is clear. It works well with my kid at home, when I used to do it with classes it was like a plague of locusts had cleared the classroom 😆
-I also found it worked better not to 'nag' but to make sort of factual statements about what was wrong, and what I wanted to see. So, say there are food wrappers around, I'd call child over 'I see wrappers on the sofa, I feel disappointed because food wrappers should go straight in the bin. I'll feel really happy if I see you putting them in the bin without being asked next time.' Short and sweet, and then pointed stare until they go in the bin. Also helps if you give them a way to earn some positive recognition at the same time: 'hmm, while we're heading to the kitchen, I wonder if there's anything else you could take to be extra helpful? Ah yes, thanks Bob for picking up the cup, that's really helpful.' Then (I guess, anyway) they come away thinking 'I tidied up and mum was pleased with me' and not 'I'm messy and mum was cross'.
Appreciate all this is not exactly effort-free, but I found it less exhausting than nagging. I also appreciate that I probably sound barmy 😆 but just thought I'd share what worked for me because I tried EVERYTHING until I came to a formula that worked, mine is now quite tidy. Good luck OP!