Your post kind of contradicts itself from paragraph to paragraph and your first paragraph I do not think is true.
You argument is that Pitt is focusing on one position and drafting purely based on that but, given that your premise is to ignore any mocks, it doesn't seem like premise you have that they have "so many failures" is actually true. Going back starting 3 years ago (not really fair to judge a pick in years 1 or 2), we have Pickett who was a bad QB, Harris who has been solid for them, Devin Bush who is great, Terrell Edmunds who has been solidly above average, TJ Watt who has been amazing, Burns has been mediocre, Bud Dupree was bad, and then before that they had pro bowlers in 4 out of their last 5 first rounds. That is a pretty solid success rate overall especially when you factor that its never in the top 10. I would actually wager its above average for the rest of the league.
Meanwhile you argue that the mocks are subjectively ranking prospects and that there is no "40th best prospect or 15th best prospect" but then use that artificial ranking to argue that the Steelers are reaching for a position. It cant be both. Either the prospect rankings mean something and they show teams reaching for need or drafting value over need, or the rankings do not exist and for all we know they view every pick as a value pick.
Lastly I think you are forgetting the Eagles have 2 of the best rookie CBs in the NFL, and Dejean looking like one of the best in the NFL already. CB is FAR from a need for them and getting one next year is a luxury as they will almost certainly be the number 4 or number 5 corner, with 2 elite players, who will be in their second year, starting for them next year. However even knowing that they will sprint to the podium to take Travis Hunter if he were magically available at 25.