Smooth scrolling is already implemented correctly in the browser. Your implementation is just a hack that hijacks the normal behaviour a user is accustomed to and just gives back a version that just feels wrong to interact with, even without performance issues.

Do the entire internet a favour and un-implement it.

It isn't broken on touchpad for me.

That said, if I'm being honest, it's fairly unpleasant to use on a desktop with a mouse. It scrolls you to the top after it loads (which is after the rest of the page), and behaves differently than the computer normally does...

I would recommend doing away with it.