Pihole is a domain level ad blocker and youtube serves ads from its own domain so like @Tiger2205 mentioned, you cannot block the ads youtube serves without blocking youtube itself.
Youtube has also implemented Manifest V3 which curtails ablockers ALOT. Chrome based browers have been nuetered pretty well. There may be some ways left to get around Googles Ads but I think the options are dwindling outside of signing up for Googles premium service. Personally I'll suffer the ads before I do that...