I know I'm late to the conversation, but I want to give my 2 cents, even if just for myself. I'm going to try to avoid getting into a blame-based analysis here, but the reasons this team has struggled post-SB is because of 1) scouting/drafting, and 2) the allocation of cap space (ie: which players we've sign to big contracts).
Regarding scouting, I sometimes wonder if the scouts forget to consider scheme/fit when evaluating a player. I look at John Simon (4th round pick) as the main example of this. It seemed like our coaching staff had no interest in using him on defense, yet after being cut in TC his 2nd year, he went on to be a solid contributor for the Texans as a depth OLB. Simon seemed like a tweener coming out of college, so maybe the coaching staff couldn't find a position for him. Arthur Brown would have been a much better fit as a Will LB on a 4-3 team, though a lack of instincts and inability to contribute on ST ultimately caused him to be inactive daily (he seems like a bust regardless of scheme). Keith Wenning had a noodle arm, which didn't fit an offense that attacks vertically. Upshaw was a poor fit, since Pees seemed to require a Sam LB who could drop into coverage. Elam was a SS who couldn't form-tackle. I'm starting to wonder if Correa will be a player without a true position on this defense, but it's waaay too early to make that call. In addition (and I think this is to your original point), our drafting seems to ignore the skill positions, namely WRs, DBs, and edge rushers. They've drafted heavily on interior DL, OL, and TE, but they've either ignored or missed on WRs, DBs, and edge-rushers (especially 5-tech DEs, but also rush LBs). They've spent a lot of picks on the RB position, but have little to show for it.
In terms of drafting, as has been mentioned and accepted by most every Ravens fan, our scouts/management have not hit consistently on picks in rounds 1-3. I think 2010 is the first really bad draft we had in the Harbaugh/Flacco era, missing on two 2nd round picks (Kindle, Cody) and a 3rd round pick (Ed Dickson)--the only saving grace was getting two good starters in Arthur Jones and Pitta. 2011 yielded 3 good starters (Torrey, Jimmy, McPhee), but they missed badly on Jah Reid, a 3rd round pick. 2012 was underwhelming: some consider Upshaw a success, but 2-down LBs can be found as UDFAs; they wasted a high 2nd round pick on Upshaw as far as I'm concerned. They also missed on Bernard Pierce, a 3rd round pick, and Gradkowski, a high 4th. KO is the only really good pick from 2012. 2013 was really bad to start (Elam and Brown), but they still managed to get 3 starters. 2014 was pretty decent, only missed on Terrance Brooks among the early picks, but they managed to get 2 starters and 2 solid depth players. 2015 is not off to a good start, and I'll leave it at that. 2016 is already looking pretty good. To compensate, they've done well in later rounds. You should also consider the starting/depth UDFAs we've gotten over that time: Tucker, Michael Pierce, Orr, McClellan, Ellerbe, Jameel McClain... did above average there.
A specific trend that has emerged in our scouting is in the southeastern area scouting. These struggles seemed to precipitate in 2008 when Joe Horitz was promoted from southeast area scout to Dir. of Player Personnel. I'm not sure who succeeded Horitz as the SE area scout, but Ian Cunningham was promoted to SE area scout in 2013. It's hard to know which schools count as being in the "southeast," but in that general area, we've drafted and missed or disappointed on the following players since 2008 (not including 7th rounders): Tavaris Gooden (3rd round, Miami), Davon Drew (5th, E.Carolina), Sergio Kindle (2nd, Texas), Terrance Cody (2nd, Bama), Jah Reid (3rd, UCF), Chykie Brown (5th, Texas), Courtney Upshaw (2nd, Bama), Christian Thompson (4th, S.Carolina St.), Tommy Streeter (6th, Miami), Matt Elam (1st, Florida), Aaron Melette (6th, Elon), Terrance Brooks (3rd, FSU), Lorenzo Taliaferro (4th, Co.Carolina), Robert Myers (5th, Tenn.St). (I'm leaving off some recent picks like Perriman because they jury is still out) Some of those players were pretty highly drafted, and when you look at our busts as a whole, it seems a larger % come from the southeast. During that same span, the players we've drafted from that region who are not busts are: Mosley, Jernigan, McPhee, and Oher (and some would consider him a disappointment as a 1st rounder). Seems like a low rate of success in the southeast. I imagine this is just the cost of everyone poaching our scouts--you inevitably promote someone who is unqualified eventually.
However, the area where our FO has struggled the most is in its allocation of cap space. A lot of this is bad luck, though some of it was unwise in context. Just off the top of my head: Webb, Pitta, Benjamin Watson, Jacoby Jones, Eugene Monroe, and Ray Rice did not live up to their contracts after signing (the Pitta one was unwise, the Rice an unforeseen event, and the rest due to unexpected injuries). It could be argued that Jimmy and Flacco are underpreforming their contracts. Justin Foresett only played last season under his extension, which is an underperformance imo. Billy Cundiff was cut 1 season after an extension, though he really only had one blunder of a kick to deserve the cut. Ngata was underperforming his contract until the year before he was traded. Fabian Washington and Foxworth were dumb FA signings. Especially over the past few seasons, we've had a lot of salary cap space allocated to people who were not performing for one reason or another. This really hurts your ability to compete in a salary-capped sport. The good news is that these contracts will hopefully be behind us soon enough, and the dead money not too painful moving forward.
TLDR, what has hurt us the most is: 1) scouts drafting players who don't fit schematically, 2) scouting has missed in the mid rounds, 3) scouting is/was especially bad in the southeast region, and 4) poor allocation of cap space. Doubt anyone reads this book lol.