I was a naysayer before I had kids, too. I now am able to get a first person view of Scratch usage through my child who likes the platform very much.

What's missing in a lot of these discussions about Scratch efficacy is the community aspect. Kids like getting a response in the comments section from their peers and many of the alternatives proposed don't have that. Without an active community, a lot of kids might never use the alternative despite being "better". In the case of Scratch (unlike Khan academy, which he completed also), he keeps using it, keeps trying things and keeps coming back because of the rewarding community interactions.