You should, but it specifically doesn’t work for YouTube. PiHole works by blocking DNS requests to known ad servers. But YouTube hosts their own ads on the same servers that host the videos. So if your pihole blocks the ads, it also blocks the videos you’re trying to watch.
Sideload uYou+ or set up Yattee. If you don't know how to do any of those things, look into DNS based ad-filtering like ControlD and install Video Lite. Or skip the DNS part and only install Video Lite, but you'll see in-app ads unless you pay the $12/y subscription.