Since your scripts are coming from youtube.com, it's not possible to only remove the unused code in this situation. You'd need direct access to their code.
The code is being delivered by a 3rd party source. In this case, it's Youtube. Even if you lazyload your videos, they will still require the necessary scripts (base.js, etc.) to load your videos.
So, unfortunately, it's not possible to alter the code coming from Youtube beyond removing your videos entirely.
JohnCodes is right in that you can't edit third party code to make it more effecient, simply not possible.
If you want to autoplay the video, then there's nothing to be done.