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.
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.