As an American whose government was formed by overthrowing this same lineage of monarchy, I can see why they want to celebrate. After 1200 years of this families ruling, with the right to be paid millions and use millions every year of taxpayer money from the poor and working classes, people still love the royal family because they put on big parties like jubilee and appear so rich and entitled that it makes their heart swell with pride. 1200 hundred years leading up to the queen's party is a lot of time to brainwash the public that a family collecting interest on all the castles and investing still needs more money from the public.
The American colonists hated the taxes sucked up by this ruling autocratic family and its rulers. So, we overthrew them. But the British general public was never so fortunate, and remained under a king or queen, a symbol of absolute dictatorship no matter how stylish the purse of bejeweled the crown.
I personally find any dictator symbol distasteful and prefer to move toward full democracy, which even we haven't achieved yet. But you have to dispose actual queens who have a "right" to suck up money from the mere talent and skill of being born. All this money spent and bestowed on her due to her sole skill of being born. That's all she had to do. Not much a reason to give one person and her massive extended family millions and million every year. Talk about entitle white woman! Even some of our extreme privileged white men in America, the ones who act entitled, can put a finger on the Queen Dizzy Liz. She just have to try like they do; she just is.