I think the biggest problem with YAML is not YAML itself but what people use it for. It's very flexible and readable for smaller files (much more than TOML - which is awful for hierarchical data).

A bigger problem is that so many things are using config files that should be proper DSLs or libraries, but no one wants to maintain a library (or create RCE as a service by accident) and no one wants to write a parser/interpreter.

Most of the "YAML sucks" issues would go away if we stopped treating LowCode as something desirable (we do actually need to write code sometimes, as it happens) and if we had better sandboxing/parser generators along with less animosity towards DSLs.