In no particular order...
1. "We can't afford to keep/sign him!"
To paraphrase the Bard, there are more ways to move cap dollars around than are dreamt of in the casual fan's philosophy. While cap money is, of course, finite, when it comes to an individual player that a team truly covets, far more often than not a team will find a way to fit the player under the cap. I recall many fans and pundits this year asserting that the Rams would not be able to keep Leonard Floyd... until they did.
2. "We drafted the wrong guy at that spot."
This statement does not, over time, always prove to be wrong. When made immediately after the draft, though, its usually a pretty sill statement. First, we don't know half of what teams' know about the prospects. We can only guess what medical reports, interviews (with the player and those who know him), and hours and hours of live observation/film review might have revealed. As fans, we can only guess, project and, of course, crow about it when the 5th round pick we said would be a star becomes a star!
3. "The league really screwed us on the schedule!"
I've read comments in the past suggesting that the league plays favorites when making the schedule. While there is, of course, a deliberate effort to place contenders and the more marketable teams in prime time/national TV spots, the suggestion that there is a deliberate effort to manipulate outcomes through scheduling decisions is a bit tin-foil-hatish in my mind. Its particularly silly when fans rail about relative strength of schedule figures at the time of the schedule release. First... within any division, the strength of schedule of non-divisional games is generally equal, with a slight stacking based upon where the team finished in the prior year. Second... a quality team last year may not be one this year, and vice versa. Is anyone that worried, for example, about the match-up with Green Bay this year if Aaron Rodgers is gone?