I’ve seen some sets that are blocks with random flat surfaces but still balanced.

However, I notice that many antique block sets seem far superior to newer sets.

(I’m sure someone must make an amazing new set, I see some suggestions in the comments).

Having made some wooden block sets from scratch, what I am always amazed about with a good set is balance / size of pieces, coupled with variety and quantity. The balance being a vitally important part that seems to be overlooked in “bad” sets.