The problem with mainstream statistical sites, like ESPN or NFL.com, is that they lay out a very basic collection of stats on a grid with sortable categories. Yards. Touchdowns. Sacks. Interceptions. All worthy for individual discussions that prompt enough debate that it keeps us interested. For example, Carson Palmer threw 20 interceptions last year. Bad enough that he was one of the league leaders in interceptions. Worse still is when you weigh those interceptions and how they impacted the game. We later discover that, including the five pick-sixes, Palmer's interceptions resulted in 22.5 points lost on offense with the defense scoring 66 points off the interceptions. But then you have to figure out, how many interceptions were the result of bad passes and how many were the result of brick-hand receivers running lazy routes? It's all about context and we could keep going. But it's information like that you will not find on the mainstream websites with generic statistical information.
Another case in point is our defense. You know that the Bengals ranked 15th last season in total defense, yet ranked 24th in scoring defense, allowing 24.7 points/game. But what you don't know is the context of that. For example, the defense didn't give up every point. Points are also scored during special teams returns and turnovers by the team's offense, amongst other things. So it's not entirely possible to have one universal stat that really tells the story. We know this. Always have. But it's also not entirely possible to weigh each play unless we spend 6-7 hours re-watching a game and doing that 16 times.
One statistical analysis you might like comes from Football Outsiders. According to their analysis, the Bengals defense forced 44 three-and-outs last season, resulting in a three-and-out on 24.9% per opposing drive last season for the entire season. That ranked 12th in the NFL. So you're asking why was the Bengals defense not particularly good last season? Mostly because of the points they allowed. Ranked 23rd in the NFL with 1.9 points allowed per drive and 20th with a touchdown/drive percentage of 20.3%.