My rule is: if I get a single notification that I find useless, I'll immediately disable that notification channel (I'm on Android; I'm not sure if iOS has a concept of channel-specific settings) for that app. Even if the channel can include useful notifications, as the article discusses. If the app doesn't bother to categorize its notifications into channels at all, I turn off its notifications entirely, and I won't…
Sadly iOS doesn't really have this in the same way :(