The idea did take off big-time, just not at the level of C++ compilers and in a more modest way than envisioned. Java and C# both provided reflection interfaces

The idea did take off big-time, just not at the level of C++ compilers and in a more modest way than envisioned. Java and C# both provided reflection interfaces to implement many of the motivating examples for meta-object protocols. Qt (user interface) and Unreal Engine have elaborate semi-automated systems for gathering metadata about C++ objects in order to manipulate them reflectively. The architects of these systems definitely took inspiration from these meta-object protocol papers and related LISP and Smalltalk efforts. Nobody quite took it all the way, and I suspect that's because the boundaries between compile-time reflection, use site checked macro programming, and declaration site checked type level programming are quite hard to pin down in such a general system.