It starts to get more verbose when you have more keys and deeper indentation since the whole hierarchy is repeated for each key e.g. [general.foo.bar.bar].
JSON wasn't intended for maximal human readability/writability like CSON/YAML were. It was intended first and foremost as a simple data transmission format.
Large hierarchies are always difficult in plain text formats. I'd argue if you need the user programming the config to understand a large hierarchy then you've already got a problem.