your comparison to yaml or ini is apt; toml's strength over yaml is syntax simplicity and toml is more-or-less a superset of ini (which itself is poorly-defined).
On a deeper level, I think they might be frustrated with the ability to develop custom formats (XSDs) which effectively make XML not one format, but a gazillion formats.
There's plenty of room for debate, e.g. element versus attribute and things get unwieldy pretty quickly [1]
The "note"-example illustrates the issue quite well: the order of the elements matters and you end up writing every element identifier twice.
Not to mention the bloat that comes with using an XML library that's actually compliant with the standard and includes all the bells 'n whistles.
with json - you just suck it all into your data structure
with xml - sometimes people put stuff as a tag, sometimes as an attribute. Maybe not you, but someone else will do it.