Every object in Qlik Sense is a "new" object. They are not just re-written, but have been fundamentally reimagined from a touch, responsive and mobility perspective. For e.g. all charts are SVGs in order to allow better rendering on the client. They are rendered in a grid to allow them to respond to practically any screen size.
It is also much easier to create new objects in Qlik Sense, so if you are missing something specific, its much easier to add it (Qlik Sense - Introduction to Extensions (video))
Finally, we do have a roadmap where we plan to add more visualizations, but that roadmap cannot be shared publicly.