When talking about the opponent, Vermeil always said they get paid too that maybe the other team deserves some credit, but even the bad teams in the NFL have playmakers and the margin for error isn't as great as records may indicate. When a team gets one top of another team, the entire momentum and game plan changes.
Plus, the other factor is a few injuries can change the landscape quickly when you have to plug another guy that doesn't have the details down on executions, one guy falls and the entire offense crumbles. It is the one thing you can say with Fisher is that his offense was so dummied down that 7-9 was 7-9 no matter who executed it.
Teams now days on both offense and defense rely heavily on scheming from week to week and when you are just plugging in one new guy the dominos start falling.
Lastly, energy is everything. Bottom line is the Titans came into a trap game and weren't prepared energy wise to compete against a bad Texans team.
But you are right that the gloom and doom fans could look around the league and see a bunch of top teams putting up some stinker games.