these places aren’t ‘banned’, there’s just a new quarantine requirement
Except that is not true.
Here is the FCO latest travel advice...
From 27 July, the FCO advise against all non-essential travel to Spain, including the Balearic and Canary Islands, based on the current assessment of COVID-19 risks in the country.
So yes, not banned but against the UK FCO advice & will impact most travel insurances. A holiday is NOT essential travel.