Teams are only as good as their latest winning season, and a lot can happen between now and tomorrow, especially in the world of sports. It is better to go with a team that will win this season, then to try to build a team for the future based on unpredictable results.
Just like everyone else in society, we all are responsible for our own actions. Whether it be finances, family, or employment, everyone should be smart about choices. If the MLB mortgages the future and jeopardizes its finances, what message is that sending to society? The message it sends is that it is okay to go into as much debt to win. As a result, this creates a downward spiral into winning no matter what the cost!
In general, I think that's a bad idea. Everyone wants to win now, but only a few teams are actually equipped to compete right away. For most teams it would make more sense to focus on the future. For certain teams that are among the best in the league, I think it makes a little more sense to focus on the here and now. However, the MLB playoffs are basically a crapshoot. The best and most talented team rarely wins the World Series, so getting a little bit better by mortgaging your future is almost certainly not worth it.
The only teams that have a justifiable reason to go all in are the Cubs and Indians. They both have a shot at the World Series this year, and their players are collectively long enough that they'll have multiple chances if they miss. I'm a Mets fan, and they should be a top of the ballot favorite to win in 2017, so all I hope is that they don't blow it by going for a one game playoff this year. The same is true for the Pirates, Cardinals, Rockies, Orioles, etc.