Actually my parents and in-laws are always saying they never spend so much time "playing", "playing is for kids, they can do it by themselves or with other kids", they always say. They may have a point that interaction with a bored parent may just kill their creativity whereas finding something to do by yourself may be a useful skill to learn. So what did they do? No idea, dad was a work and reading the paper at home while mom did stuff around the house I guess.

Perhaps we are just imitating commercials of happy families running in fields of flowers.

It also gets easier, my son is getting quite into mountain biking, can't wait until he fits a proper one with gears and proper brakes. Finding that stuff that you and your kid really both enjoy is pure gold.

Given how much freedom I had as a kid (a lot, my earliest memories include me running around outside unsupervised), I think that kids can and should play by themselves or with other kids as much as possible. As long as there is a safe environment, I don’t think kids should need constant supervision.