I know that code.org's lessons have a "view the real code" box, helping to ease one into the "here's how to think about problems and structure, but here's the actual JavaScript that underpins it". If you haven't tried that, it may help
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