Well, there's an easy explanation for that: The Cardinals are in the playoffs so often because they're GOOD.
That, and their division is TERRIBLE. Slightly better lately, with the Pirates and Reds getting their shit together a little, but come on. In 2006, when they won the WS, they won their division with 83 games. Would have been good for about 8th place in the AL East. Out of 5 teams. They've been decent for quite a while, but that crap division certainly helps.
As for the Red Sox "always being in it", it may see that way, but last Post-Season appearance for them was 2009 (swept in LDS by LAA). May seem like they're always there, but they haven't been. 2003-2009, excepting 2006, was a good run though. The Blue Jays spent the money, they're just a terrible team. They were the favorites to win the division and so some damage this year, and they shot themselves in the foot. Repeatedly. Money /= good. And I think the Red Sox proved that Farrell wasn't the problem last year for them...
And the Yankees: not sure where the optimism is coming from. They're already locked in as super-expensive, and are losing a bunch of big pieces. They've got several expensive guys that are liabilities at this point, and like a 4 person logjam to try and DH them. Best player is a FA at the moment, and their best hope for getting better is that their most expensive player gets suspended or hopefully banned from baseball. Only 4 years, 116 million left on that one! Jeter can't stay on the field and hurts you when he does, Mo retired, CC looked terrible this year (4 years 96 million left there), Texiera has another 3/67.5M left on his deal, can't stay healthy and has wrist issues sapping his power. Kuroda, your best pitcher, is a FA. Pettitte retired. Granderson's a FA. They have NO farm system, without any 'big' prospects, and their best guys took steps backwards this year, so no help coming there.
In all reality, who would you say is the Yankee's best player right now (excluding FAs)? Gardner (.274 avg, 8 HR, 24 SB)? Nova (9-6, 3.10 ERA, went from 16 wins to 12 to 9 the last 3 years)? Right now, Cano is all they've got, and while he'll probably return, it's not guaranteed. He leaves, there's literally nothing there. Especially for the 189M they're going to try and get under. This has happened a few times in the last decade where we thought the Yankees might fall off and they held it together, but it's starting to seem more and more like the bill for all the bad and expensive signings is starting to come due...
2009 was a good year!

So right about my Yanks. What an off-season this will be.
We just might NOT see Cano in pinstrips again.
I believe I heard Karoda was ging to retire?
Still have Michael Pineda. That should be a good rotation fill.
Easy on El'Capitan... he lead the majors in hit before his injury. I'm concerned... not sure he'll make it back. He's had a year to recover and couldn't make it back... I'm hoping he can heal properly. When healthy is is NOT a liability in the field at all.
What do I want to see?
Tex at first and the wrist thing healed.
Granderson resigned patroling in the outfield with Gardner and Soriano.
Jeter healthy back at short stop.
A-Rod dies and we find someone, maybe just throw Nix or Nunez in there.
Let either JR Murphy or Auston Romine work behind the plate. Cheap and given a huge opportunity. While I like Stewart behind the plate, I think he's a proven <.250 hitter.
Rotation... ?????????

CC will rebound. 18-21 wins. Gain some weight back man!!
Pineda finally gets in the roation. win 16-18
Nova has the potential to win 20... I saw big strides in his head at the end of this year.
David Phelps wins 15-18
5??? Who knows at this point.
With Mo gone (sniff) everyone is talking David Robertson for the closer. I don't thinkn so. He's FANTASTIC at what he does. I wont root against him, but I don't see him succeeding in that role.
So, closer???? Who knows
We won 85 game this year with a band-aid line-up, our ace not pitching like an ace and Hughs and Jaba failing.
A least we got Girardi back...
LOTS of questions for sure.