Being a full time baby would not be fun.
A baby does not really do much but sleep, cry, poop, eat, get fed and maybe crawl around and cannot do much.
Even a toddler does not get to do much and has to stay close to the parents, has to be watched, cannot go outside by themselves, cannot take a walk by themselves etc.
I would not give up my adult life to live as a toddler or a baby.