They tried to fix this in Android, having apps create separate channels that users can enable and disable at will. Then no app makers used them because there's no real incentive to do so. Sigh.
Is that true? I think all the apps that I had to partially enable notifications I managed to do so. To the point that I started to wonder if Google is requiring it as part of the app review process
They are used but they definitely don't enforce strict separation (which of course doesn't scale, but they could at least penalize apps that get reported by users for violating it). In most apps there is one notification channel that has both the important stuff you want and some marketing garbage.
Long time Android user, and it works great. Not sure why your experience is so different, but I'm very happy with the notification channels experience.