I don't know if I have the definitive answer, but I can tell you a few areas I think we are struggling in that are self-inflicted...
1) Depth is certainly an issue, but you can't have Tate Wildeman, CJ Smith, Casey Rogers, Ronald Thompkins, Nick Henrich, Chris Hickman, Javin Wright, and Myles Farmer all have significant soft-tissue injuries stunting their development. You then compound that with guys like Adrian Martinez, Mo Washington, Wandale Robinson, Luke McCaffrey, Cam Taylor-Britt, Noah Vedral, and Miles Jones all missing game time due to injuries, and that's a huge reason you are struggling to create depth.
2) I don't think we look great in space. I stated in another thread, arguably our 2 best sides on each side of the ball haven't been big in our S&C program Mo Washington (barely lifted), Wandale Robinson (hurt most spring and fall so laid off), Darrion Daniels (transferred in during the summer), JoJo Domann (rehabbed at home all summer), and that's not a great stat. Couple that with guys like Adrian Martinez, Matt Farniok, Boe Wilson, Jack Stoll, Brendan Jaimes, Ben Stille, Mo Barry, Tyrin Ferguson, and others looking worse, that's not great.
3) When the staff got here, fans were imploring Frost to keep Keith Williams due to his recruiting. But besides defensive back, that was the least deep position group on the roster, so it was tough to sell that. The staff needed to overhaul quickly, but that is a position in 2019 that is an issue. Why? 2018 recruiting class had 6 WRs in it. Justin McGriff, Katerian LeGrone, and Andre Hunt are all gone. Dominick Watt never made it to campus. 100% of the freshmen WRs you brought in from your first class are now gone. The other 2 WRs are JUCOs who made little impact in Jaron Woodyard and Mike Williams. You can't do that.
But other positions are that way too. What about RB? We brought in 3 guys from the 2018 class. Mo Washington, gone. Greg Bell, didn't even make it a season. Miles Jones, gone. It's a transition class, I get it. But for our 2020 roster, we will literally have zero players from Frost's first class still on the roster at RB and WR. That's not a Riley culture issue.
4) I think the team psyche gets screwed up when they are publicly called out on how they need talent upgrades and how bad we look. When it was happening, I thought it was weird to go there because many of the guys you were saying weren't good enough were who you were going to be calling on to win games in 2018 and 2019. In 2020 close to 80% of the roster will be Frost's, time to start looking ourselves in the mirror instead of blaming other coaches or ADs (I already think it's time but i'll give a pass).
5) Play-calling needs to put our players in positions to win. Just two examples, but defensive personnel matching so I don't have to hear PJ Fleck or Jeff Brohm say they exploited our LBs. Go look at the conversion rates of 3rd and 5 or more against those two teams and Indiana. We aren't getting home on the pass rush which means it's only a matter of time before the RB outruns Barry, Honas, or Miller. Secondly, I give Scott Frost some leeway when people are mad about play-calls due to RPOs not necessarily being a run or pass call, it's what the defense gives you. But i've been advocating for more 2 TE sets since fall camp, TE was our most proven commodity (besides QB at that time), and it only made sense to me to keep 2 TEs on the field when you know what you are going to get from them. But for some reason, we continue to go 3 and 4 WR sets, and then complain we don't have depth there. At the goalline, as many have mentioned, why not put 2 TEs there, especially when it's working against Purdue? You don't have to change your offensive philosophy to do that, you literally just have to call the plays to your teams strengths.