After 2 seasons with Frost as the head coach, I think much of what you said is true. Here are a couple things to consider...one in defense of Frost and one that may not speak as well of him.
1. Frost inherited a Nebraska team that was 28-23 in the four years before he arrived and with one bowl win. It was not a great stretch over a 4 year period.
2. Frost inherited a UCF team that went 31-21 in the four seasons before he arrived including a Fiesta bowl win and a top 10 finish to the 2013 season.
At Nebraska the culture was starting to go downhill with some of Pelinis antics and the transition to Riley was not smooth. Riley dug things into the ground all around.
Meanwhile at UCF Frost took over for a coach who had many strong seasons at the school and that resulted in fewer transitions for the players brought in the back in 2014 to 2016. Thus he had a better culture with better talent and everything worked out magically in 2017 despite not having recruited most of the players who made an impact.
In summary, was Frosts 2017 season a true depiction of his coaching aptitude? After seeing these past 2 seasons I feel too much weight had been placed on that one season. But, he also inherited a bigger mess at Nebraska so he does deserve another season to show significant improvements in the program.