I also used to believe that Lisp is super-powerful when I was using it. But it isn’t, really. Not when compared to Julia, and a lot of other languages. It is practically impossible to write portable, reusable, and fast code in Common Lisp the way you can routinely do in Julia.
I don’t think that the Julia package ecosystem is “fragmented” because Julia is, in some sense, too powerful, and this does not encourage cooperation. I see cooperation happening organically across the ecosystem — it is just that the process is, naturally, slow.
Many packages that seemingly address the same thing are actually very different. Take, for example, my favorite plotting packages, PGFPlotsX.jl: it works through the TeX package pgfplots, with all the advantages and disadvantages that implies. The former include very close integration with (La)TeX documents, in terms of content and style. I don’t think that this package can be meaningfully merged with any other plotting package.
I am not sure what you mean here. A lot of packages work fine with a significant part of the ecosystem, because Julia’s design allows a lot of more-or-less orthogonal composition.
Part of the problem may be user expectations: people coming from other languages may expect to see a big über-package doing everything under the sun, while in Julia they will encounter cooperating ecosystems, of which Tables.jl is an excellent example (there are many others). This may be confusing, because using Tables just gives you some minimal functionality, and conversely, for most functionality you will not be using Tables.
I can easily imagine this being very confusing to an R or Python user. But the solution is just learning the ways of Julia.