Eagles racked up a ton of yards but ranked near the bottom of the league in red zone scoring percentage.
Makes sense to me.
Exactly. This is why it's important to look at a range of stats, not just the traditional ones - underscoring that you need to take a comprehensive view of stats, and see them in context, to draw useful conclusions from them.
I'm not really a football guy, but I would think in addition to the offensive and defensive scoring numbers TieClark cited, you'd also want to look at red zone completion percentage (as you suggest), as well as differentials in sacs/sacs allowed, penalties, turnovers, time of possession and so on. No doubt there are lots of more advanced metrics for football I've never even heard of. (God knows I've barely begun to understand the plethora of advanced stats available in baseball...).
Each quality stat (as opposed to the football equivalents of unreliable/non-indicative stats like errors or RBI) provides another facet which, collectively, can paint a much more thorough and accurate picture of how teams win or lose games.
The goal of advanced stats is to capture as many of the individual decisions and actions that go into determining the course and outcome of a game, and to identify formulas by which those events can be understood and manipulated to generate realistic aggregate projections over a suitably long timeframe (like a season). Of course, this is much easier in baseball where each event occurs in isolation with a discrete number of participants contributing, and where "a season" provides 162 games' worth of data - a much more statistically significant sample size than you get from 16 NFL games.
Either way, though, the stats can help us understand what's going on - and can be particularly useful in identifying outliers or trends that can be exploited. But they merely augment and clarify the information you get from watching the games - they don't replace watching.