I have observed the Makefile effect many times for LaTeX documents. Most researchers I worked with had a LaTeX file full of macros that they have been carrying from project to project for years. These were often inherited from more senior researchers, and were hammered into heavily-modified forks of article templates used in their field or thesis templates used at their institution.
This is a great example of an instance of this "Makefile effect" with a possible solution: use Markdown and Pandoc where possible. This won't work in every situation, but sometimes one can compose a basic Beamer presentation or LaTeX paper quickly using largely simple TeX and the same Markdown syntax you already know from GitHub and Reddit.
That won’t solve any problem that LaTeX macros solve. Boilerplate in LaTeX has 2 purposes.
The first is to factor frequently-used complex notations. To do this in Markdown you’d need to bolt on a macro preprocessor on top of Markdown.
The second one is to fine-tune typography and layout details (tables are a big offender). This is something that simply cannot be done in Markdown. A table is a table and if you don’t like the style (which is most of the time inadequate) then there is no solution.