In building Responsive sites, there's the "site" you build before the site – that is, the structure or framework that allows the site to adapt/respond, and then the finished website itself... content, images, functionality, etc. that exist within that framework.
RLM provides an easy way to create the framework....no need for SASS, LESS, preprocessors, Node.JS......If you've got a good understanding of HTML/CSS and Media Queries, you can quickly build your site's responsive structure.
There are some users on here who have gone straight from using CC's WYSIWYG site creator to RLM and have got responsive sites up and running now without having to first learn Bootstrap, Skeleton, Foundation, etc. or a lick of SASS.
https://www.callendales.com