[gwbas1c]

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.

[nflekkhnnn]

The old and new json lib is written by the same person. The newer one is a bit more low-level — that’s intentional, the old one was too bloated.

[gwbas1c]

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.