The only working way to change YouTube interface to new Material Design 2017
Google Chrome Example
Put this command to your Developer tools Console if you don't care about your current preferences:
document.cookie="PREF=f1=50000000&f5=30&f6=17;path=/;domain=.youtube.com";
If you want to save your current preferences then watch the video. Template of console command below:
document.cookie="PREF=_______________;path=/;domain=.youtube.com";