I also recently learned that Brilliant uses block-based lessons, too, so there's obviously some there-there
I would guess that a lot of the problem is one of actualization: how does one go from solving "someone else's problems" to one of realizing their own ideas. Based on what I've seen, I'd guess that a Minecraft mod port that maps blockly down into lua would go a long way toward "do some things that materialize change in an environment that is familiar." I haven't used Roblox, but I believe it's similar so if they have a programming language, same-same. I started to suggest using Valoren <https://gitlab.com/veloren/veloren#get-veloren> since it's actual FOSS and thus would be much, much easier to integrate into, but I haven't played it in order to know how much uncanny-valley it would have with any preexisting Minecraft experience
Tangential, but kind of related, a lot of the first "real" programming was in monkeying with webpages, since "view source" used to go a long way toward showing how any cool trick was done. I guess the risk to that approach is that kids may not care very much about swooshing colors or alert("hello") but it for sure is accessible. I can recall typing Basic programs out of magazines to get a game running, but I don't actually recall what happened from there in order to know if "learning by transcription" is helpful or just feels rote