The right reason to hate XML would be some technical limitation or technical issues with it. But XML works quite well and is reasonable powerful. So the complaints usually boil down to: It is ugly and verbose.
I mean, it's also a taste issue. The verboseness is ugly. I don't like it.
But it's a technical issue. You have to parse all of that verbosity, every time you read it, which is inefficient. If you're hand-generating it, which happens in the development process, you have to get all of that verbosity right, or it doesn't work. These days nobody hand-rolls a parser, but the interface to the parser is more clumsy than it needs to be, because it mirrors the structure of XML.
I mean, it's also a taste issue. The verboseness is ugly. I don't like it.
But it's a technical issue. You have to parse all of that verbosity, every time you read it, which is inefficient. If you're hand-generating it, which happens in the development process, you have to get all of that verbosity right, or it doesn't work. These days nobody hand-rolls a parser, but the interface to the parser is more clumsy than it needs to be, because it mirrors the structure of XML.