Yes, Guile is not minimalistic, and Guilev2 is a further step away. In particular when you are not designing a system from scratch but just looking for a simple way to extend an existing system with some programmability not bringing a whole lot of its own complexity into the game, Lua might be a better choice. Guile is moving into the direction of a system foundation rather than a system extension. That is basically its positioning for getting into Emacs, and that is getting more and more the way in which it is integrated with LilyPond.
But it is not exactly the niche of "extension language" that it is mostly being advertised for.