I've always used diaper rash cream on my newborns when they were sleeping to protect against diaper rash because at night they would be in a wet diaper longer than normal during the day.
However if the newborn woke up crying in need of a new diaper I would change it even if it was not full because I wanted my newborn to be very comfortable and wouldn't want to be in a wet or poop diaper either.
Diaper rash cream is not required for any baby but it's a good idea to use it especially if you use cloth diapers.
As long as you change the babies diaper often enough and wipe and clean them up you should not have any problem with diaper rash.
But using diaper rash cream is perfectly okay for newborns or any age of a baby or toddler.
Diaper rash cream is a good diaper rash preventative measure so it can be worth it to use it because when a baby or toddler gets diaper rash it's very uncomfortable for them.