A bit like Kaliborio above me, I've never been treated 'like a baby' but my needs have meant I needed babyish things.
Doctors told my folks to expect me to never learn to be able to do many things for myself but to try anyway, so they did.
They changed me until I was 12ish, then less and less. One difference was that pullups had been introduced and I could look after myself for short times in those. The other was I eventually learnt to change myself. Until then they changed me, aunties, grandparents, friends - all sorts. At home, I was never shy about nappies and those and long t-shirts were pretty comfy wear. I tended to get lost in what I was doing and was very in the habit of being checked rather than asking. It was never presented as 'baby' just, 'Rosie'.
My folks still put a plastic mat under the chair where I eat when I visit them and i still favour spoons to eat with and ask for my food to be cut up for me. If going out to a restaurant with friends I'll ask them discretely. I have a 'splash zone' in my own place where I eat.
I had a lot of toys for younger children to try and practise my hand-eye skills, general co-ordination. Shape sorting and bead stringing and that. I've always had an overactive imagination, playing with teddies and dolls and things till I was 15/16. Then starting again when I was in my mid-twenties.