For those in the "need graphics" bandwagon, keep in mind that the core of DF is simulating the world.
For those who has suffered with FPS death, can blame all these world calculations from a falling log that causes cave-in far below that you have not even open line of sight yet.
And to take a game like Rimworld using basic graphics developer kit, is not an apples to apples comparison.
RimWorld takes a smaller scope of tracking finite objects, and then feeding that to the engine (Unity / Unreal?).
Shit, I don't think an graphics engine like that can render a playable FPS to simulate the many parts of a creature that can procedurally be change their status.
I mean, look for an instance of a minecart shotgun full of various gold crafts. A golden scepter not only hits a troll, but shows details of punching through its large tunic, breaking a false rib, causing the troll to skid back. The same scepter continues it destruction decapitating a goblin 3 tiles behind and to the right of the first troll. But we're not finished, because the gold scepter ends up lodge in the marble block wall that is now smeared in blue troll blood.
In Rimworld. Shoot pistol, miss, miss, hit, hit, target down. Cursor over to target, bleeding, left lung punctured, left kidney missing.
That's the difference. DF has ability to 1 step simulation, and keep track of the objects in its x,y,z coordinates.
No current affordable 3D graphics engine, if any, is optimized enough, to crunch and simulate and render all of that in 1-step meaningful display.
Perhaps not even a CPU fast enough to do so.
It's possible to simulate a subset of those objects, and that's how those other games approach it. It's DF like, but sacrificing the depth of details.
Likewise, when objects are limited, it is then manageable to create a UI for the many possible decision-trees.
DF does not compromise the number of those simulated creatures. You have 100 dwarf, 100 goblins, 100 pets, a megabeast spewing syndrome on all 300, all 300 will have to calculate those effects.