Plus there is the cumulative impact of Human/Vulcan interaction. It was the Vulcans who were the other party in Earth's First Contact and they played a leading role in the 98-year period from 2063 to 2161 when Earth, with Vulcan's help:
- picked up the ashes after WWIII
- achieved global unity,
- became a spacefaring species
- launched extra-solar colonies
- fought humanity's first interstellar war, and
- gave up a good deal of sovereignty to embrace collective interstellar and inter-species unity by forming the Federation.
And then there were all the things the Federation went through together. All in the past 300 years.
This against a millenia-old genetic tie and interstellar migration that passed into faint memory and near-legend by the 2100's (Earth calendar) plus the fact that Spock sees Romulans as "Fallen Vulcans" who need to be brought to Surak.
Sometimes I think it's Spock who needs the attitude adjustment, not the Romulans.