One of the important things implementations failed to do was properly support Schemas (http://yaml.org/spec/1.2/spec.html#Schema). And this is still the case today. Had they done so, the safe load issue would never have arose, and the loaders/dumpers would be properly configurable to suit the needs of the application, e.g. don't support "Yes" and "No" as `true` and `false`.
I once did about 98% of the work to support Schemas properly in Psych (https://github.com/ruby/psych) but the maintainer said he didn't want to "maintain it".
So, there you go. What else can one do? You can't blame the spec for decisions of implementors.
(That's not to say the YAML spec couldn't use some improvements, but it's far from "not so great".)
I once did about 98% of the work to support Schemas properly in Psych (https://github.com/ruby/psych) but the maintainer said he didn't want to "maintain it".
So, there you go. What else can one do? You can't blame the spec for decisions of implementors.
(That's not to say the YAML spec couldn't use some improvements, but it's far from "not so great".)