Fair question. I also own the 3 games you mention (although I haven’t played Raiders for a while) and I think like many light-mid weight Euro’s there are commonalities beyond the base mechanism of send worker to slot on board and gain benefit of slot. Examples being the end round pressure of feeding the tribe (family), the culture card set collection (quest completion to match Lord’s alignment).
What IMHO is Stone Ages point of difference is the resource collection mechanism. Rather than being a constant it’s linked to a random dice roll. Each worker allocated to a resource collection space is represented by a die. Furthermore each resource has a different divisor ranging from Food = 2 to Gold = 6. So send 3 workers to collect food and roll 10 and get 5 food. Same workers, same roll with gold and receive 1 gold.
There are ways to mitigate the dice rolls and ease the burden of feeding the tribe by purchasing tools which allow a die rolled to be increased, increasing the number of tribespeople (dice) and growing fields to provide ongoing food so it’s not a total luck fest.
For me it’s that element of chance on each resource hunt (and throwing dice) that keeps the game engaging. There’s also a nice tension with having to be mindful of securing the points from the limited houses (victory point cows) available in the game.
At the end of the day though - yes it is in that light-medium game space. Compared to Dune Imperium it’s only ever going to be more of a filler. In some ways it is a shame it published when it did so close on the heels of DI.