Given that Boimler had only been to three planets (not including Earth or stupid Vulcan), despite serving on the Cerritos for a year, makes me think that they hadn't had crazy adventures every week until just now. And Envoys was a simple escort mission (nothing crazy about a drunk Klingon) and this week's episode had a bog-standard moral dilemma that none of the lower decks crew cared or thought about.
During the Rage Virus, the first crazy adventure we see, Rutherford seems to tell Ensign Barnes that "this stuff happens every week" (paraphrase). This could be because Rutherford might be relatively new to the ship. He's a "recent Cyborg" (of a few weeks), so it might be that his injury was incurred on some other ship and he was on the prior transfer before Tendi. Barnes may have been on the transfer with Tendi.
And of the three crazy adventures we have had (Rage Virus, Gelrakian Boarding, Terraforming Emulsion), all three could've been easily avoided and were caused by shipboard incompetence (Ransom not being screened, giving the Gelrakians the wrong totem thingy, the rival ship getting destroyed because they wanted to be in control).
