Being dark is also a property of planets, and these dark stars did not have the same massive gravitational field black holes have, in that they were supposed to

Being dark is also a property of planets, and these dark stars did not have the same massive gravitational field black holes have, in that they were supposed to be able to shed light on nearby planets. So they had very little in common with actual black holes, mechanically, including not being holes in spacetime (which is what makes black holes such an interesting problem). And, again, they also operated in a completely different way by attracting the mass of photons, which doesn't exist, rather than bending spacetime. I'm not saying there aren't similarities, but this ancient idea of invisible stars is a relatively simple thought experiment that only hints in the direction of black holes. For the most part, all the important properties of black holes were not predicted.