The last monarch to refuse assent to an act of parliament was Queen Anne in 1707.
She would rather be Queen than be right.
Well, that is what modern constitutional monarchy is about -- staying around by not exercising direct power.
A monarch who habitually refused assent to legislative acts would quickly become an ex-monarch.
Look at what happened to Queen Anne's father, uncle, and grandfather.
So you’re claiming that there’s no check on the tyranny of Parliament.