"Are you seriously saying it means anyhting except Mum at home full time?"
No. I said nothing of the sort. Sorry to disappoint you!
I think 'optimal' care is provided by one care-giver, preferably mum or dad if they are happy or willing to do it. Loving and engaged relative next best. Next best a good nanny or childminder. Who will stay around for a while.
Least best is being cared for by nursery nurse on a 1 to 3 ratio in a nursery with a high staff turnover.
I'm talking about babies by the way. Not 3 year olds, for whom a pre-school setting and group childcare is, in my opinion, developmentally appropriate.
Of course parents need a break and children are resilient little creatures. Good parenting goes a very, very long way to make good the damage that inappropriate childcare can do, so most babies don't suffer any permanent damage.
But I do have massive issues with very small babies doing 50 hours+ in nurseries, particularly those with high staff turnovers, as many nurseries in London do where I live. I don't think it's a good or developmentally appropriate form of care for tiny babies.