I never got this stance; JSON sucks for config files, because as a user, if there is anywhere that I need and am more thankful for comments, is in a configuration file. And TOML is maybe a good substitute for INI formats, but it doesn't really support nested data like JSON would, so suggesting to use TOML instead of JSON is misleading except for the simplest and most basic needs.
If replacing JSON is the objective, I'd very much rather recommend HJSON [1] than TOML.