Not sure why you think it has to be that way. I author LaTeX documents using org mode. Org mode handles most of the boilerplate, and I can still put pretty much any custom LaTeX within the org document, wherever I want it (this includes \newcommand, etc). I lose nothing by going to org mode, and I gain much in terms of reduced boilerplate.
My absolute favourite moment with that flow was a client who wanted one as a docx instead of a PDF. Pandoc obliged and they commented that I must have spent a lot of time reformatting things for them :)
I'm curious now though... maybe I'm missing out!
I think your parent comment was saying that LaTeX alone is sufficient. You also seem to be saying that LaTeX alone is sufficient while using Org mode. Would you please clarify if I am interpreting your comment correctly or not?
I'm not saying either. The parent said it's easier and cleaner to use LaTeX all the way. I was pointing out that it is easier to write in a format like Org mode and export to LaTeX (whether via Pandoc or Org mode's built-in exporter).
Of course LaTeX is "sufficient". It is also, IMO, painful.
If one is going to write LaTeX code anyway, it seems easier and cleaner to use LaTeX all the way, move all the boilerplate along with the personal template to say, a file named preamble.tex, and \input{preamble.tex} in the documents.
However, there are situations where Pandoc can be convenient. For example, I wanted a document[1] to be written primarily as README.md (CommonMark format), so that GitHub could render it as the project README. At the same time I wanted to render a PDF output from a customized form of the content. Pandoc is convenient for cases like this although it takes a bit of work to fine-tune the formatting and customize the content for each output format.
[1]: https://github.com/susam/gitpr
[2]: https://github.com/susam/gitpr/blob/master/Makefile