I agree that only a handful of blue blood teams can take a loss and still make the playoffs. ISU is not one of them. This is also the biggest reason the playoffs need to be expanded.
We haven't seen many non-blue blood teams make the CFP, period. In the seven years we've had it, Washington, Oregon or Michigan St are the three worst 'brands' to make the field. All three won their conference and had one loss, for the record.
In fact, of the 28 bids over the 7 years, 17 have gone to 1 loss teams. Of those 17, just three went to teams that didn't win their conference - Ohio St in 2016, Alabama in 2017 and Notre Dame in 2020.
On the flip side, only three P5 teams that won their conference but had one loss have been left out - Baylor and TCU in 2014 and Ohio St in 2018. We all remember how the Big XII bungled 2014, but three of the four teams to make the field had one loss, so two were going to get left out no matter what. Similarly, Oklahoma made the field in 2018 along with three undefeated teams, so a one loss conference champion was going to get left out no matter what.
Could a one loss ISU get in with a conference championship? History seems to indicate we have a pretty good shot, particularly considering the Big XII should be much stronger than the ACC and PAC this year.