I don't think there's a cookie cutter answer to this question. In some cultures it's normal for families to live together, with multiple generations and extended families. In western culture it's usually seen as a case of moving out being a part of becoming an independent adult. Some leave in their mid or even early teens, others never leave. Sometimes those extremes and anything in between can be healthy, sometimes anything on that spectrum can be unhealthy.
If you have bad parents (as I did) it's probably better to get out ASAP, but sometimes for various reasons that can be difficult. My family home, if you can call it that, stopped existing when I was 20 and for a couple of months I lived in a car before finding work and somewhere to live. A couple of years later I moved in with my mother so I could afford to go through uni, but that was basically a case of living in a share house with someone I had little emotional attachment to, didn't ever share food/time with, etc., and I was just there for the cheap rent. After finishing uni I moved interstate, hated it and moved back to my home state.
I've seen people in their teens who really badly need to move out of home. I've seen people living with their parents as well as their spouses and it has been perfectly happy and healthy. I've seen people in their 40s and 50s living with their parents and it has been utterly tragic, especially when they're single and clearly emotionally dependent on their parent(s) and unable to form healthy relationships away from their parents.
The bottom line is that if you're happy and able to make good friendships and relationships outside your family, and are living with your parents by mutual choice or at least in mutual happiness rather than emotional necessity on one or both sides, there's no problem regardless of age. If it's financial necessity it's obviously not ideal, but if it's emotionally healthy there's no big problem.
Western culture has a strange stigma about living with parents. In many cultures it's thought of as bad for children to move out of the family home until they're married, or even after they're married. If I had decent parents (which I don't) I would be happy to live with them (or I suppose it would end up being more them living with me) as long as there was space for them to do their thing and my partner and our kids (if/when we have them) to have our own space, as is normal in many traditional cultures. Being white Australians I expect my kids will want to leave when they're somewhere in their early 20s or so, but as long as they were emotionally and functionally independent and healthy and financially comfortable I would be happy for them to live with me as long as they wanted. Realistically I think that's extremely unlikely to happen, and I'm perfectly happy with that. If they were too emotionally dependent (to the point of it preventing them forming normal relationships with other people) or trying to stay at home as a means of avoiding financial accomplishment, for their own good I would kick them out as young as was legal.