Injuries are a part of any sport but cannot be predicted, depth wise for starting pitchers we have to trust youth, that is true. I agree purchasing more pitching depth would be a wise move; however, when being realistic about the team we root for and the payroll constraints imposed on them it becomes pretty clear that it will not be happening. There is good potential in the young arms in the minors.
Once again - the strength of this team lies in the big 3 starters (who haven't been prone to injury during their careers) and a dominant bullpen. Kopech, Crochet, Stiever, etc. Could be leaned on in an injury situation and there is still developmental potential with Cease.
The issue I would see burying this team is if one of Giolito, Lynn or keuchel was injured going IN to the playoffs. At that point you still can game plan Cease/Kopech followed by the pen winning you enough games to get back to the big guys. Is it perfect, no, but with a dynamite offense behind those guys, there's still a chance.