The Wildcard can sometimes yield good story lines. There's no question that the Florida Marlins were a good story line. And sometimes a team that's a Wildcard is playing as well as anybody, or better, come August or September.
So, the objection of the Wildcard was never that a Wildcard team wasn't good enough to be in the post-season tournament or couldn't win it.
The objection, for thoughtful fans was, that it destroyed the concept of a pennant race. As long as you have a Wildcard you can't have a true pennant race, because there's not an "all or nothing" aspect to finishing first in your Division, unless the pace of the Division is so slow that first place team would have lesser record than the Wildcard.
Otherwise, the Wildcard undermines the excitement of a close divisional race that goes to the wire. And, it actually penalizes teams that win their divisions in a blow-out, like the Braves or the Giants, because they get no significant advantage once the playoffs start over a mediocre division winners or the Wildcard. That's the real objection.
The contrast between that, and let's say, football - could Wildcard team go to the Super Bowl? Yeah, and God bless them if they do, because they have to go a tougher road - they have to play an extra game - they're on the road all the time. Whereas teams that do better during the regular season get a first-round bye, perhaps, which is a huge advantage. Then they have homefield throughout the Playoffs, and since Playoff round in football is only one game, that homefield is 100%. It's not one extra game out of 5, or 1 extra game out of 7.
Now, they're (MLB) never going to change this playoff format, at least not in the next couple of years. Because, by luck, this playoff format this year, coughed up the Red Sox, the Cubs, the Yankees, and a great story line with the Marlins; and all the Series went the limit; and they all had compelling story lines. And so, if they fiddled with the format, the superficial reaction would be, "Hey, why are you messing up a good thing?" But, it's exactly the same format that produced relatively uninteresting post-seasons in the past, and relatively low ratings on television in the past.
What they (MLB) really should do, is seed the playoffs in a way that makes sense. Not eliminate the Wildcard necessarily, but create a distinction between being the Wildcard and being a team that wins its Division.