Earlier quoted context omitted.
An interesting perspective I've heard is that she should have been more political in a few extreme cases. She is the head of state and her actual job should be to bring left and right together in the very controversial, almost unsolvable issues, and get them sorted out. She should really be like a couples therapist for political leaders. She never did this. She always stayed out of politics.
There's a reason for this, I'm a bit vague on the details, but when Parliament took control of the country from Charles II, one of the agreements was that the monarch would keep out of political affairs.
It's not just about the constitutional precedent - it's a strategy the monarchy follows for its own survival. Politics is by definition divisive; if the Queen publicly takes a side on the issues of the day she'll alienate half the country, which is a surefire way to hasten the demise of the monarchy. She's free to have her private political opinions, but it's very much against her interests to express them.