If you're just youth staff your main job is standing in certain areas, making sure kids don't damage themselves or others, if you're entertainment host you're running a lot more of the activities/shows, but that's quite a different job and requires more of an acting/performing background.
You tend to move around every half an hour or so. Your day might be something like: stand outside the bathroom, then stand at the top of the slide, then check kids in, then stand at the bottom of the slide, then back outside the bathroom, then support an ent host with science or other activities, then run a game of gaga ball, then back to outside the bathroom again... and an hour of cleaning at the end of the day. (When I moved lines we gave a quick go over but then housekeeping came in for a deep clean at the end of each day which is something I could see Disney doing when they start sailing again)
I personally couldn't go back to it, I'm too used to running full sessions instead of the odd game and getting to know kids and their families and being busy and feeling valued. Disney was a lot more of working hard, hardly working lol, easy money tho and you get to say you work for disney.
If you go to the nursery there's obviously a lot more responsibility, and its pretty much the same as working with that age on land, different kind of hard work in there, but unless you're nursery staff it's rare you'll be in there, maybe a couple of hours over the whole contract.
Teen staff is a bit more intense too as again, your running it and there's less staff, but you do get to know the kids better. It can be hard if you have the more difficult kids as you never see the parents. If anything happens between the kids, it falls back on you, so like the nursery there's more but different responsibility.
When I worked there I thought YS at Disney was the best thing ever, but I'm definitely more an activity based person, so found i was much better suited and much happier elsewhere.
A while back I did a comparison of the Disney and royal clubs. While it's a comparison and focuses on 2 cruise lines, it also gives a lot of details of how they run, which might give you a bit of an insight of what it's like to work in them. Obviously its all pre covid and I have no idea what it will be like going back, especially as some of the changes for the UK cruises effect the kids clubs. Its over on the Royal page, but here's a link:
https://www.disboards.com/threads/my-comparison-ish-of-royals-and-disneys-kids-clubs.3756878/
If you have any questions feel free to ask, its been a while for the
DCL kids club side of things, but basic ship life doesn't really change even on different ships or with different companies...