Maybe you're a bit negative because you've seen it more than once or since you were going. For me the stones were a lot bigger than I had pictured them. Can only recommend it.
There’s thousands of parks and other beauty spots in the U.K. which are far more memorable and to which you can spend hours strolling around, take kids of all ages to, and generally enjoy a day out at. The Stonehenge, while historically significant, is an anticlimactic tourist attraction and an even worse beauty spot.
But maybe if/when they build a tunnel for the A303 they might then do more with the available space and so it becomes more of a family attraction rather “just” a monument.