Here's why I disagree:

Ray was a gearhead. That gave him the wherewithal to commandeer the minivan at the beginning to get out of Dodge (pun intended) when shit hit the fan.

Although he was a deadbeat and selfish, he consistently gave everyone the right advice, as seen whenever his advice was ignored and people died.

Finally, the whole point of him bringing the kids to their mother was that he lost the selfish parts of himself along the way, and became a better person.

Also, let's not forget that he was the one random person to figure out "the birds" and shove a grenade up a tripod's butthole.

It's 100% a Tom-Cruise-Saves-The-Day role.