This is a great comment, I've had exactly the same experience. For a simple, concrete example of the fragmentation issue, the canonical JSON parser seems to be JSON3.jl, but there's also JSON.jl, which is slower and has other subtly different behavior. Neither mentions the other in its documentation, neither is deprecated, but if you search for "json julia" only JSON.jl comes up on the first page of results, but if you ask a question about JSON.jl in Discourse or Slack they'll probably tell you to use JSON3.jl instead.
(To be fair, Postgres has an extremely similar issue with JSON data types and it's doing fine.)
The state of tabular data formats is similar but instead of 2 libraries there are 20, and some of them are effectively deprecated, but they're not marked as deprecated so the only way to find out that you shouldn't be using them is, again, to ask a question about them in Discourse or Slack. You can check the commit history, but sometimes they'll have had minor commits recently, plus (to Julia's immense credit) there are some libraries that are actively maintained and work fine but haven't had any commits for 3 years because they don't need them. I assume this will get worse before gets better as the community tries to decide between wrapping Polars and sticking to DataFrames.jl, hopefully without chopping the baby in half.
I feel like the "not invented here" mindset contributes a lot to that fragmentation. It's easy to write your own methods for types from other Julia libraries because of multiple dispatch, which seems to have resulted in a community expectation that if you want some functionality that a core package doesn't have, you should implement it yourself and release your own package if you want to. So we have packages like DataFramesMeta.jl and SplitApplyCombine.jl, not to mention at least 3 different, independent packages that try (unsuccessfully IMO) to make piping data frames through functions as ergonomic as it is in R's dplyr.
Despite all of this, I still like the language a lot and enjoy using it, and I'm bullish on its future. Maybe the biggest takeaway is how impactful Guido was in steering Python away from many of these issues. (The people at the helm of Julia development are probably every bit as capable, but by design they're far less, um, dictatorial.)