Yeah, I would strongly advise all general managers to develop their own in-house talent and have someone ready to step up at every spot. Quite unfortunately though, that plan tends to get all buggered up at one sot or another. At times like that, teams have to turned to FA, trades or do the hell without. Teams like the Yankees. Red Sox, angels, etc. just reach in their pockets and pull out an endless stream of cash or just grab a couple of guys off the bench, from the pen or down on the farm and they trade them off for what they need or even deal them to someone for guys to deal for someone.
When you get down to teams like the Reds with pretty limited resources, you have to look ahead, decide a year or two in advance who you're going forward with and extending, who you're not and trade away the surplus for something else you need. You constantly churn your roster trying to anticipate and avoid dog-snarls (like having 80% of your rotation leaving via free agency). Major inefficiencies like that, tying up your resources on unnecessarily on the bench, in the pen, etc. otherwise you may have to do without