I had a similar issue with the NYT - every time I subscribed (and during my subscription period) I found it impossible to avoid getting on their spammy email lists if I ever logged in to read articles. The only workable solution I found is to pay my 1-year subscription fee, immediately cancel the subscription, and then use the NYT in incognito mode thereby stopping them from caching my read article count and avoiding having to login (I would always accidentally login if I maintained the subscription). It’s annoying, but I want to give them money while also avoiding being harassed by dozens of emails every month. Sadly there is no similar work around for youtube.