The banner isn’t just there for show. Only when a visitor accepts cookies can you begin to track them with analytics. If they refuse to accept cookies, then you can’t start your analytics tracking. This go/no-go can be configured through Tag Manager
GDPR Check - What we can do
Review the cookie banner so that it complies with the current GDPR legalisation using Tag Manager
If no banner exists, or it’s simply ‘decorative’, that will be corrected.
Review the sites forms and the data retention from those forms.
Review the policy documents, Cookie and Privacy. Again, if they don’t exist, they will be created.