If you're not going for it in today's MLB environment, you're -- well, let's not say "tanking" and go with "developing." Teams that build from their farm system through the draft, the international market and trades of veterans for prospects keep reaching and winning the World Series.
The Kansas City Royals had the No. 1 farm system in baseball in 2011 and won two pennants, including a World Series championship in 2015. The Chicago Cubs hit the top five in 2013, ranked No. 1 in 2015 and won the World Series in 2016. The Houston Astros had the No. 1 farm system in baseball in 2014 and won their first title in 2017. The Boston Red Sox just won a World Series with homegrown former top-100 prospects at all three outfield spots, third base and shortstop and used three other top-100 prospects to trade for Chris Sale and Craig Kimbrel.
I don't think any of this is a big coincidence: Teams can't buy championships. They can buy a player or two to finish off a good roster, but the bulk of a pennant-winning roster comes from within, either through cheaper players the team developed from its farm system or veterans acquired by trading such prospects. Winning the farm system rankings can feel a bit like winning the offseason. It doesn't guarantee success -- now or in the long run -- but it's better to start with a whole boatload of young talent in your organization when you're building toward a championship run.