People making mistakes implementing a spec is not in itself a good reason to drop it.
It is when the mistakes are frequent enough, obviously implementing RSS feeds is rather hard and most sites are really poor at it.
Adding to that is the simple fact that very few server languages have really easy or good XML generation at this point, compared to JSON library support. There are lots more good JSON libraries around and people are more comfortable with them and used to how they work.
There will be malformed JSON, that's to be sure.
Why, when most JSON will be produced by a library that simply maps something out to JSON? Also it's super easy to check JSON validity. If you ask 100 developers today to produce a defined output in JSON and XML, which do you think will have a much higher percentage chance of being correct?
Do you escape slashes? Are true and false quoted? How long can a number be? Do the numbers use decimal dot or decimal comma â" or does it depend on the locale?
Why do you think any of that matters? If the JSON is valid it is valid. Everyone on earth and most libraries are used to accommodating JSON that may have true or false either as boolean values or as strings for example. It simply doesn't matter.
I agree, that JSON is easier to read than XML, but not easier enough
It's WAY easier to generate in a world of developers that uses mostly JSON now and hardly touches XML. That alone is a HUGE reason to switch. Why saddle every website on earth with legacy crap? It's probably a big part of the reason RSS is not as common anymore, and the real crime would be if most sites had nothing like RSS at all...