Sometimes a weaker SOS can deceive you. OSU had a poorer SOS than us last year but they were the better team that night.
High SoS can tell you for sure whether or not a team is good. We know Alabama is very, very good. Low SoS can only tell you that a team might not be as good as they appear. Low SoS of course does not mean a team is not good. I do think it matters in terms of resumes as well though. If you didn't play anyone, you didn't beat anyone, and if you didn't beat anyone, do you deserve a place in the playoffs? I'd say Clemson did but it shouldn't be automatic that just winning puts you there.
But... with Ohio State... even Boise State, and Alabama, SoS also means something else in my opinion. With Ohio State last year, they played a soft schedule most of the year, and they also stayed healthy. I see the two as having a link, not necessarily one that is always the case, but if you play a soft schedule it's easier to stay healthier than if you play a tough one. In the case of last year Alabama was beaten up, Ohio St. despite the quarterback issues was one of the healthiest teams in the country. That mattered on the field, for instance at linebacker Alabama ends up with a true freshman in there due to multiple injuries, and that leads to one of Ohio State's biggest plays. Also, with Boise State we saw a team that by no means demonstrated the ability to navigate a tough schedule, but like a car tuned for drag racing, showed great ability in bursts.
So, there this hidden value sometimes as well. We can for certain if a team is good based on SoS, but also much like a player who has been well rested throughout the season, there's that fresh legs off the bench type scenario that can play out as well. If I had to choose, I'd prefer Alabama have a bit soft SoS to be honest.