Many JavaScript frameworks and libraries are converging to concept of "web components"
but standardization is quite slow, so web code and content is not reusable.
If original web was so diverse, complex and custom, it would have never taken off with all benefits.
The actual challenge is not efficiency of web development, but multi-modal communication,
including voice, VR, AR, MR etc. Smart web content should be able to auto-adapt for available interface, including M2M API-like communication.
Shadow DOM
Spec: Shadow DOM - W3C Editor's Draft
Tutorial: Shadow DOM 101 - HTML5Rocks
Custom Elements
Spec: Custom Elements - W3C Editor's Draft
Tutorial: Custom Elements v1 - Google Developers
HTML Imports
Spec: HTML Imports - W3C Editor's Draft
Tutorial: HTML Imports: #include for the web - HTML5 Rocks