The EU defines personal data as:
‘personal data’ means any information relating to an identified or identifiable natural person (‘data subject’); an identifiable natural person is one who can be identified, directly or indirectly, in particular by reference to an identifier such as a name, an identification number, location data, an online identifier or to one or more factors specific to the physical, physiological, genetic, mental, economic, cultural or social identity of that natural person;
Thinking about Google Analytics: Provided PII is not pushed through a website's URL, then Google Analytics's only way of identifying a user is through their IP address, but GA has the ability to anonymize their IP Address.
So if there's no way to see "any information relating to an identified or identifiable natural person" because their IP address has been anonymized, then do you need a user's consent to enable GA on your website?