but...if I already have my CV in LaTeX why would I need it in this?

Hi, HMR author here -- HackMyResume treats LaTeX as a destination format, not a source format! So you would generate LaTeX through Handlebars/Underscore or whatever other template engine, then use your normal LaTeX workflow. Currently for example, the "awesome" theme generates a LaTeX CV based on Awesome-CV (https://github.com/posquit0/Awesome-CV). You have to run `xelatex` or similar to finish the build, which should probably be documented better.