The notifications usually indicate the source app or service, if not calendar.
To control those: Settings > Notifications > shut off everything
Weather alerts are either from an app (see above) or from a government weather entity. To disable those:
About emergency and government alerts - Apple Support
Government alerts (at least in the US) cannot be blocked.
More generally, switching to either the Assistive Access interface for a “more focused features and a simplified user interface”, or switching to a flip phone, can avoid much of the complexity inherent in iPhone, too.