Both you and yummyfajitas are making the classic error of falling for cynical pop-science just so stories. This evolutionary psychology and biology stuff applied to humans is still pretty new and pretty far from "well established biological fact", and it comes with all the caveats of human behavioral research plus the added trappings of being a scientific fad.

In particular, there is plenty of room in evo-psych for pair bonding and long term relationships. Historically and across diverse cultures these relationships have generally been the dominant method of producing children, so I'd say it's a pretty OK evolutionary strategy. The 'scientific' evidence is all around you, evolved bag of meat.

And in long term relationships, effort is not optional.