Yes I let my toddlers wear just a diaper in the house or outside when it's warm outside.
However in public such as going to the park, stores etc the toddler has pants or clothes over their diaper.
It's not that hard to put shorts on over the toddlers diaper when going in public and I always keep extra shorts and pants in the car and in the diaper bag in case the toddler leaks pee out of the diaper onto the pants or shorts.
At home or in your yard it's fine for the toddler to run around wearing just a diaper as long as it's warm enough.
However in public diapers should be covered up.
I hate when I see toddlers in public wearing just diapers.
The toddler looks cuter wearing pants and clothes over their diaper.