Sometimes circumstances don't allow for a consensus national champion. In 1997 both Michigan and Nebraska claimed a NC. They did not play each other, so nobody will ever know who was better.
In 2017 we have the same situation. We see both UCF and Alabama claiming a NC. The CFP invitational tournament did not make room for the only unbeaten FBS team. Therefore Alabama and UCF did not play each other and nobody will ever know who was better.
In 1997, after we beat Tennessee in the Orange Bowl, SF pleaded for at least a share of the NC. He did not do that after beating Auburn in the Peach Bowl, but he could have. NC's can be shared.
We had a split NC in 1997. It did not bother me at all. We have a split NC in 2017. That does not bother me, either.
It does not have to be one or the other. Just like in 1997, a NC can be shared. One can recognize both Alabama and UCF as 2017's national champions.