Yes it's OK to keep your baby in a diaper all the time.
Babies wear diapers all the time and for 24 hours per day 7 days per week without issues.
If your baby or toddler didn't wear a diaper all the time and they were not potty trained then you'd have pee or poop all over the place.
A baby or toddler who is not potty trained and not wearing a diaper will poop or pee on the floor or the couch or whatever they are sitting or laying on.
You could allow a baby to go without a diaper for a few hours per day as long as the baby is laying on a towel or something to absorb the pee or poop.
But it's perfectly okay to keep your baby or toddler in diapers 24 hours per day 7 days per week.
Just make sure you wipe their bottom and private areas to clean pee and poop off of them and change the diapers every 2 to 3 hours to keep them clean and dry and they will be okay in their diaper.