I disagree.
A poet uses imagery to help paint a picture or convey meaning. If the reader doesn't understand, or misses the poet's message, then the imagery isn't working as intended.
There are poems where interpretation is open, so your argument holds good in some instances.
In my stanza, I want you to use the imagery to build the picture. You have some of it, but add a bit of Druid, you might see what I do then.
Jx
Ps. Where oh where did you get the idea I didn't know what imagery is? Surely you've read enough of my poetry by now to ascertain I have a modest grip on its implications.

In responding to Wesley, who is struggling with indirect imagery, I said it was something the more I thought about the less I understood, meaning it's sometimes better not to overthink things.
I think Druidic influences extend a bit beyond Stonehenge. In fact Stonehenge never even crossed my mind. We had them here in Yorkshire and indeed they were documented by the Romans in the early centuries. Human sacrifice at Druid hands was also documented by the Romans. Now the Romans were not above using propaganda for their own ends, so it may well be fiction. My rock is a real rock about 10 miles from where I live, called The Druids Altar. It is in an area rich in Bronze Age settlement, with many existing cup and ring marks still visible. It is also on a Roman road and has been recorded by a visiting Roman as a dire place used for human sacrifice.
Fact or fiction, it makes great inspiration for poetic material.
Again, a quick google of Druids Alter brings up a host of leads, all suggesting sacrifice, and Stonehenge doesn't even get a look in.
I studied Roman Britain, and the British Bronze and Iron ages for my degree, so am on home ground here.
Take care young Ian and may the ghosts of dead poets and long gone druids bring light to your poetic soul.
Jx