Yes it's normal for a 5 year old to still wear diapers.
While most 5 year olds are potty trained and no longer need to wear diapers at least during the day it's normal and okay for a 5 year old to wear diapers whether at night or in the day.
At 5 years old they still may have wetting accidents during the day and may need to wear a diaper to keep their pants dry.
Or at night some 5 year olds wet the bed and having them wear a diaper will keep their bed dry and their clothes dry.
My 5 year old boy wears diapers at night and in the day as he's prone to wetting accidents.
He uses the toilet and is potty trained but he wears a diaper because if he doesn't he will most often wet his pants as he's always peeing a little even before he gets to the toilet.
When away from home he always seems to wet his pants because he doesn't make it to the toilet in time.
So my 5 year old son is always in diapers during the day and night.
He prefers the diapers instead of pull ups as he finds the diapers more comfortable than pull ups.
My 5 year old son wears the Gentle Steps size 7 diapers which are perfect for him and are very absorbent.