Are you kidding me? The Texans have only been a team since 2002 (only 7 seasons)
The Panthers have only been around since 1995 (14 seasons), so making the playoffs 3 times in 14 years (more than 21%) is not bad.
The Ravens have only been a team since 1996 (13 seasons). So they have made it to the playoffs about 31% of their seasons.
The Jags have been a team for 14 seasons also and have made the playoffs 6 of those years- a strong 42% of the time.
The Saints have made the ployoffs in 6 of there 42 seasons- roughly 14%.
The Cards do have it pretty rough though, they've been in the league since 1920 and have made it to playoffs only 7 times (including this year)- that's less than 9%!
The Bills have been in the NFL since 1970 (I think that's 39 seasons, I could be wrong though) and they have made it to the playoffs 13 times (about 33%). I'm not including AFL years, since for all the other examples we're talking about only NFL years.
While 33% doesn't seam bad, the important number is that all of the teams you cited have made (or in the case of the Cards will make) the playoffs this decade, with the exception of the Texans but the Bills playoff drought is longer than the entire history of the Texans franchise. Just saying we fans have good reason to be upset.