JSON is a messy format, you'll always have to know your requirements well to be able to pick a fitting parser for it.
Are you going to parse a simple, small key-value-structure? Pretty much any library will solve it for you or you could invent your own simple parser.
If you need to stream gigabytes of complicated JSON and do sophisticated transformations back into JSON or something like that, then you'll have to evaluate several libraries and have a look at how they translate into CL datatypes. Some might reduce a combination of false, null, the empty list to NIL, which could lead to information loss and surprises.
This piece is enthusiastic but a bit subjective. I personally had zero troubles with JSON in CL, just chose one library and use it. Would also disagree with some his recommendations, e.g. Drakma has a lacking interface for error handling and Dexador is nicer for use in prod.
Is the JSON situation any better now in 2024?