I think it is a mixture of fear and laziness. No one wants to stick their neck out and entertain the possibility that Prime is doing exactly what needed to be done. College football is still very much a morality play for a lot of reporters, so fear very much comes into play.
OTOH, as Darth and you point out, laziness is a major part of the equation as well. How hard is it to look at Sean Lewis' resume and conclude he is a significant upgrade at OC? The research takes five minutes. Same with Kelly. Or that adding two 5* corners to the secondary just might represent a talent upgrade?
The fear and laziness are at the heart of it.
No offense intended but I think sports journalist tend to have a lazy streak to start with. They are the guys who would rather follow sports and be fans than go out and do something hard. There are exceptions but in general I think this is the case. They could look up the stuff you mention but that would be work and they don't even know where to start.
The fear comes from the laziness. The more things stay the same the easier it is for them to get their story and look smart doing it. Mix things up and change them and they have to learn something new before writing about it.
For someone from the outside getting a read on what is happening in Boulder is very hard. Consider that we follow it closely on a daily basis and most of us aren't confident that we really know how good they are as a team or individuals.
Add to this that Prime isn't making it easy for anyone to get that read. He has done a great job of keeping the Buffs front and center both locally and nationally but has also made sure that little of substance actually gets out.
There are loads of videos, lot's of SM content, Prime on this show or that show but they have controlled everything getting out. We don't see 11 on 11 scrimmages, we don't see formations or adjustments. Even the plays they show on the videos are ground level and from angles that nobody can see anything but the route and the catch.
Then add that Prime while dominating media is also not doing favors to the media. He doesn't make their job easy by telling them how good he thinks players or the team are, he doesn't even do the normal coach speak about good day/bad day of practice.
Beyond this he doesn't look or act like a traditional coach, he is a proud Black man who doesn't try to hide being Black or being confident, no fake humility there.
And a lot of the college football world doesn't take CU seriously. They have sucked the past 20 years mostly finishing at the bottom of the conference.
In some ways CU never did fit into the PAC. It isn't on the West Coast, it doesn't try to act like a bunch of Olympic/non-revenue sports are a big deal, it is less snooty academically that some of the older PAC schools. The traditional rivalries aren't there and never got built.
At the same time even though CU had a lot of success in the Big8/12 it never fit in there either. It wasn't located on the plains in farm country, it wasn't "country" or "Texan." A lot of those schools and their supporters look at CU as that liberal outpost where everyone smokes pot and skis.
Now Prime is shaking everything up and these reporters don't have the easy answers. They don't want to look bad by liking it and not being able to explain why. They don't want to stick their neck out in case it fails. They don't like being in that position where they come across as not knowing.