Stone Circles - Mostly Just Ritual Space?

I was just watching a documentary (Standing With Stones) on the stone circles and burial chambers of Ireland, and they started off with Carrowmore in County Sligo. It seems that the very first standing stones and burial chambers in Ireland were "dolmen circles", and the ones in Carrowmore date to between 4300 and 3500 BC, and possibly even as far back as 5400 BC.

These dolmen circles consist of a dolmen with 5 orthostats and 1 capstone creating a burial chamber in the shape of a pentagon. Enclosing each dolmen is one or two circles of 30-40 boulders.

As the documentary shows, the final dolmen at Carrowmore became fully enclosed, establishing a trend towards bigger & bigger burial mounds and eventually massive passage tombs like Newgrange.

What interests me the most is that these boulder circles are quite likely the first ever stone circles, and that means they originally were used to demarcate burial zones. With time, although plenty of monuments were still enclosed by circles (standing stones, boulders, pits, ditches), most dolmens were not, and most standing circles had nothing within them.

I suggest that originally people used dolmens to bury their dead, and the boulder circle separated the sacred space from the world - and within this space they conducted rituals of burial and/or remembrance. At some point the need arose for a ritual space that was not where ancestors were buried, for purposes other than burying or remembering ancestors. Perhaps this is where fully-fleshed pagan religions began - with a multi-purpose ritual circle?

Modern pagans still revere the pentagon / pentacle. And witches still sweep clear and "cast" a circle for conducting rituals within. Could these be remnants from as long ago as 5400 BC?

After years of looking for more esoteric explanations, I now figure that the primary purpose of stone circles was to mark a ritual space. Their locations, which I also hoped might have significance, could also be explained by something as simple as "it has a nice view", or "it was a flat spot near where we lived".