1. Allen Newell at CMU AI built a system called Lstar that was only for "Greenspuning", it was a language for bootstrapping up higher languages. It's very hard now to find even a mention of this on Google. This was decades ago.

2. I recently have been spending time learning and using the Go language from Google. It has almost no facilities for booting new languages. Nowadays that's called building a DSL. The thing is, Go is very useful, efficient, and easy to learn. Plus, it has an excellent system for concurrent and parallel programming. They explicitly decided against building in facilities for DSLs, as they are seen as making systems hard to understand.

Alan Kay wasn't wrong, he had a particular point of view. To me, today, Kay's view seems old-fashioned compared to Go. Both Go and Kay's OOP are very sophisticated. In very different ways.