TBH, that is something I am going to explore as I go on in the Amalgam Universe series.
Most cogniscent life would depend on an extended childhood for learning. This leads to a need for nurturing, which means more effort spent on fewer young.
Cogniscents who have litters would be rare. And possibly level 5 Deathworlders.
Civilisation also, to some degree, requires an element of co-operation to progress. You need a certain amount of trade and specialisation to get into space. Naturally competative species would likely stay on their own planet. And possibly blow themselves up.