I can't be the only person who thinks the monumental effort spent on config formats is bike-shedding.
JSON is good enough for anything I've done. Not perfect, but no serious flaw that can't be fixed by just adding a simple app-specific post-process step that I will inevitably do for any other format anyway. JSONSchema gives us some typing sanity.
Can we just move on already to more interesting problems? It's not like git fulfills every VCS wish I've ever had either, but I have to move on. Projects and libs that introduce new config formats that continually remake the wheel, whose quirks have to be learned, are not helping my net productivity.
But if you use those extensions, all your tooling breaks.
(Aside: I think the real bike-shedding would start when you want to add some syntax for raw string literals, e.g. heredocs; it's one of those features that feels redundant, until the day when you really need it and you can't bear the pain of repeatedly escaping and unescaping.)