As far as the age thing, I would note that DeBoer's 2023 Washington team had 26 5th and 6th year seniors. I think Michigan was similarly stacked in terms of veteran players, and it is notable at least in terms of DeBoer's team that these were primarily 3 star players. I think about half of those guys were 6th year Covid seniors, so it was a pretty old team and DeBoer is certainly familiar with the concept.
I don't think people should over-react though. Cignetti did it that way because of limited resources, and so did DeBoer as well, he wasn't recruiting well there. The flip side is that Indiana despite the age gap still only beat Ohio State by 3 points.
The key is balance in my opinion, don't go too hard on recruiting when it's primarily for depth. Don't rely too much on the portal because it's harder to build around portal additions and that can lead to instability. Don't forget the downside, Deion famously leaned hard on the portal, produced instant results going 9-4 then fell to 3-9. His last recruiting class was ranked 73, if you miss on the portal under those circumstances you are in trouble.
This is where Cignetti is pulling away from the pack. It isn't the formula that's so much better, it's his evaluation. He's finding the gems in the portal, that's the key here. If you find the right recruits you can build a really strong foundation and if you can find the right portal players you can build off of that foundation. Cignetti was able to use JMU players for his foundation in this case. He brought 13 players! So those were his guys, his "recruits". DeBoer brought 4, and while those have all been impactful that's a heck of a lot less.