How to use only scripts from new theme?

Your code does seem ok, so it is hard to guess why are you not getting expected result. One thing to note is that WordPress ships with its own copies of Backbone and Underscore, it is considered a good practice to use its copies in such case.

The scripts you don’t “need” are likely coming from core and/or plugins you have installed. Which probably have their own opinion on what they need to work.

So in the end one strange part is why are you not getting some of scripts you enqueue.