alt Hacker NewsLua was specifically designed to be a configuration language https://www.lua.org/history.html
Lots of people start out with a non-programmable config format. But, as their situation becomes more complicated, they end up shoehorning in programmable-ish features until they realize they are running straight into https://en.wikipedia.org/wiki/Greenspun%27s_tenth_rule and decide to do it properly.
I mean, fair enough I guess. I've accidentally more-or-less reinvented interpreters on two separate occasions (both times using JSON as a quasi-AST), so I understand it.
I guess I just feel like if you feel like you need programming constructs in your configuration, its approaching it from the wrong angle, and it should instead be handled via plugins.
I feel like configuration itself should be a "dumb" format like JSON, and when you want to do anything that can't be accomplished by plain JSON, you should allow for easy development of plugins.