Earlier quoted context omitted.
LaTeX is complicated and verbose. Markdown and YAML are terse and readable. Also, separation of form from content makes life amazingly simple.
I agree that separation of form from content makes life amazingly simple, that's one the main virtues of LaTeX. :) As I said before, preferring Markdown and YAML solely on account of syntax seems fair to me.
My approach is to abstract all style-related concerns in a template and keep the content in dedicated files: YAML for structured content (CVs and invoices) and markdown for prose-like content (letters).
Beside making life easier by using formats more suited, syntax-wise, for the particular type of content I'm dealing with, this opens up new possibilities for automation (e.g. I can iterate on repetitive data structures, for example for building an invoice table) and ultimately results in DRYer LaTeX code in the template.