It's September 1st, and the Diamondbacks have a record of 63-68. To get to 89 wins, an arbitrarily picked lower limit for a playoff spot, the team would need to go 26-5 with the remaining schedule. The Diamondbacks aren't going to go 26-5.
I don't say that with any hint of malice or glee. I wanted them to make it, too. Maybe you didn't, and, okay, that's fine. I think most fans thought it would be a long shot, and it made for an exciting August.
There exists in sports fandom the role of 'smug realist.' You know the type: always looking to bring the mood down, lacks imagination, feels a compulsion to inject a "reality check" every chance they get. Sports can be tough, so it's just one coping mechanism among many. It's just one of the more annoying.
Think about this, if you're angrily composing a comment to counter the above: the Diamondbacks were playing meaningful baseball in August. I'll take that over last year every damn time. They were playing meaningful baseball and it was fun. And it'll continue to be fun, because there's a good amount of fun players on the team.
I'd love it if the Diamondbacks could be in the playoffs in the year. But here's some realism for you: they won't. Over half the league won't be playing meaningful October baseball year. And frankly I'm not watching baseball just for October. If I was, I'd just tune in then and call it a day. Baseball can be frustrating in the day-to-day, but it can also be exhilarating, and draining, and most of all fun.
So maybe you were sitting in the corner, grumping it up in August while the Diamondbacks flirted with Mount .500 and maybe a playoff run. It's safe to come out now. September's here, and the dream is over.