There exists a peculiar amnesia in software engineering regarding XML. Mention it in most circles and you will receive knowing smiles, dismissive waves, the sort of patronizing acknowledgment reserved for technologies deemed passé. “Oh, XML,” they say, as if the very syllables carry the weight of obsolescence. “We use JSON now. Much cleaner.”
You are clearly one of those people that never had to deal with xml in a production system. Even with proper syntax highlighting, dealing with xml is a nightmare, whether it’s for configuration or data transmission. People switched to JSON because it’s better. Period. And that’s an incredibly low bar to set, because I don’t think JSON is that good either.
Like another person said, all of these features of XML doesn’t make it nicer, it makes it worse, because it means you have to be ready for any of those features even if they’re never used.
There are really good uses for XML. Mostly for making things similar to HTML. Like markup for Android UIs or XAML for WPF. For pretty much everything else the complexity only brings headaches