When one sees a report about a British megalith in a BBC or other media article, the words "our ancestors" occur frequently. "What were our ancestors doing here?" or "It's important to understand what these stones/chambers/axes meant to our ancestors." Technically, you could say that a small percentage were ancestors of current Brits, or taking it the other way, that a small percentage of the ancestors of current Brits were them. But mostly, the people who built the megaliths were wiped out by the Bell Beaker tribes, the Celts, the Yamnaya. The mtDNA suggests that some few females were spared and taken as wives, or slaves, or concubines. A very few. The Celts used Stonehenge, and likely some other stone circles, cursuses, or megalithic sites, but they didn't build them.
As we increasingly take disease into account in understanding history, we are applying that to prehistory as well. In northern continental Europe there is evidence of plague preceding the arrival of steppe tribes that mostly replaced the descendants of the Eastern European farmers who had moved there a millenium or two before. It is likely that the steppe invaders had some partial immunity to plague, which went before them, weakening the occupants. This was so complete in Britain that it is believed to be a 90% population replacement.
Secondly, the first speculation - often by the archaeologists, not just the reporters - of any new site is "It could have been a temple." Yes, it could. But it could have had another main purpose such as stadium or playing field for blood sport. Some contain remains of pigs that were killed with a bow and arrow, after all. Also, they might have served multiple purposes. If it was a solemn religious place, it might also have been where many tribes met to discuss alliances or strategy, as a reminder to keep promises made before the gods.