Until not long ago when creating themes for WordPress I made the serious mistake of trying to create everything from scratch, and from scratch I mean from take care of using correct semantic tags to having a file structure as clean as possible avoiding structure duplication in files.
I also have to add that the structure of my functions.php files were very poor, which led me to lose the benefits of using a CMS like WordPress, for example the functions wp_enqueue_style and wp_enqueue_script to name a few. All this happened to me I think due to my little interest (or ignorance) about the projects or repositories with existing boilerplates in large communities like Github.
Recently I have had the opportunity to continue projects started by other people or to maintain other themes for WordPress, there I have known projects like _s or FoundationPress which already offer a good enough base or that are a good starting point to consider when creating themes for WordPress , so I decided to create Bubble,
Bubble is a personal project, a fork of _s, by default the structure of Bubble is integrated with Bootstrap, so you will notice that the menu for example has a walker to show the menu with the structure of WordPress. The layout is also structured with the Bootstrap classes.