It was kind of stupid but kids loved it, and probably it didn’t hurt them at all.,
I was working in a group home for what we used to call “retarded” adults, and we watched it every evening because it really calmed them down. My kids, too (we were resident managers) would all sit out there and just kind of forget about everything except this fantasy nice world, So I don;t see that it was harmful at all.
I always found it mind numbing, but it’s true that for small children with dysfunctional mothers and no daddy, Mr. Rogers was the only adult in the room that wasn’t screaming at them all the time.
A little piece of sanity in an insane world.