JSON and XML are basically syntactic variant of the same data storage strategy [:tree of attributes and children]. [1]
Where XSLT shines, and JavaScript currently has no equivalent afaik, is in transforming a tree into another one, rule-based.
The lack of support of XSLT 2.0 in browsers is a major issue, as it includes many solutions to problems absolutely not covered by XSLT 1.0.
[1]: xml2dict/dict2xml is an implementation of exactly this duality.
XML allows multiple trees in one file via namespaces, this is a big difference
> The lack of support of XSLT 2.0 in browsers is a major issue,
... for who?
XSLT 2.0 is a failed language, only Michael Kay could implement it in the paid version of Saxon and that because he was the editor if the spec, so he did as he pleased.
People stuck with XSLT 1.0 [or worse, javascript] as your tree transformation engine
Yeah, just because browser vendors put XML tech in maintenance mode doesn't mean that it wouldn't be nice to have.
We might see real world usage of these technologies had browser vendors not frozen them out.