The TL;DR of this entire thread (and answer to the question posed in the topic title) should probably be:
"Not with Pi-hole, sorry!"
Ultimately, youtube video ads are served from the same content domains as the videos themselves, so the only sure fire way to block ads on youtube is to block youtube all together 
Personally (and I mean personally - this is often a controversial option for whatever reason) I pay for Youtube Premium family, primarily for Google Play Music/Youtube music for myself and 5 other family members - as an added bonus.. no ads on Youtube. However I do understand that paying for a service is not an option for some people.