There are still virtually zero good XML parsers but plenty of good JSON parsers so I do not buy your assertion. Writing a good JSON parser can be done by most good engineers, but I have yet to use a good XML parser.
This is based on my personal experience of having to parse XML in Ruby, Perl, Python, Java and Kotlin. It is a pain every time and I have run into parser bugs at least twice in my career while I have never experience a bug in a JSON parser. Implementing a JSON parser correctly is way simpler. And they are also generally more user friendly.
Take a look at C# / dotnet. The XML parser that's been around since the early 2000s is awesome, but the JSON libraries are just okay. The official JSON library leaves so much to be desired that the older, 3rd party library is often better.
Oooh, then it makes sense why there isn't a good set of layers:
XmlReader -> (XmlDocument or XmlSerializer) generally hits all use cases for serialization well. XmlReader is super-low-level streaming, when you need it. XmlDocument is great when you need to reason with Xml as the data structure, and XmlSerializer quickly translates between Xml and data structures as object serialization. There's a few default options that are wrong; but overall the API is well thought out.
In Newtonsoft I couldn't find a low level JsonReader; then in System.Text.Json I couldn't find an equivalent of mutable JObject. Both are great libraries, but they aren't comprehensive like System.Text.Json.
JSON parsing is pretty much guaranteed to be a nightmare if you try and use the numeric types. Or if you repeat keys. Neither of which are uncommon things to do.
My favorite is when people start reimplementing schema ideas in json. Or, worse, namespaces. Good luck with that.
This is based on my personal experience of having to parse XML in Ruby, Perl, Python, Java and Kotlin. It is a pain every time and I have run into parser bugs at least twice in my career while I have never experience a bug in a JSON parser. Implementing a JSON parser correctly is way simpler. And they are also generally more user friendly.