[devoply]

Drupal 6 and 7 use Drupal crap function-based programming (not functional programming) style which over time leads to maintenance mess as you have tangled interdependencies of modules which are not 100% in terms of test coverage or quality. Drupal 8 bootstraps on top of that mess OOP. Drupal is engineered as garbage and gets unwieldy pretty quickly if you are going to be doing custom programming and straying away from the main modules. However for your case it's foreseeable you could stick to views and content types, and templates to customize those and not have to stray too much into actually writing custom code, however the UX of that sort of thing in Drupal is still shit and trying to customize that makes you do it the Drupal way which is often ugly and complicated. PHP 7 is a modern language I recommend a modern PHP framework or a modern Python framework like Django. In the end use what your technical founder knows best. Drupal makes it seem as if it's going to cut down on work, in the end it leads to more work to maintain, scale, and keep adding features and creating a better UX experience which users have come to expect. These days I would probably use some language for the backend and make the frontend with a responsive javascript framework like Angular, React, etc.