In Scotland, Wales and Northern Ireland the Union Flag is a reminder that the UK countries are ultimately run by England, where there isn’t a true acknowledgement that the countries are culturally different, let alone able to rule themselves.
Within England the St George’s Cross has become a symbol of exceptionalism and superiority, not least because it is prominently flown on nationalist and supremacist marches. Since the Union Jack includes the other countries in the Union, use of St George is often seen as a snub to the other countries.
So England can’t win? No. Correctly so, IMO, because of history and context (I am English).