1. Lo-Dash and Underscore overlap with ES5 for a few reasons. First, it allows them to support environments where ES5 functions aren't available. Those are becoming less common but still exist. But the other big reason they overlap is that Underscore and Lo-Dash both outperform native functional methods by a significant amount. Unintuitive but true, see my comparison from a few weeks ago [0]
2. It's worth thinking about who this library is for. The support for common JS and highly modular nature of the library make it seem like it is focused on Node first. But the value in a smaller library becomes much more clear in the browser where page weight matters.
These aren't meant as criticisms, it's good to see new ideas. But it's worth thinking about what niche you're filling when you develop a library like this.
[0]: http://benmccormick.org/2014/11/12/underscore-vs-lodash/