In Trek they generally need genetic manipulation to get cross-species offspring, to the point that that not being the case for Bajorans and Cardassians opens quite a couple of interesting questions. Vulcans and Romulans are probably also compatible don’t look at me do I look like a nerd with a canon encyclopedia.

The Progenitors were introduced to explain why just about everyone is bipedal and two-eyed, but the seed dropped 4.5bn years ago, every species went through plenty of evolution of its own. Yes, birds have four limbs and two eyes just like us but we aren’t genetically compatible.