Jeff Baker signs with the Marlins. So what? The Nats like Tyler Moore and he's not going to be as bad as last year. Overall, what does Jeff Baker get you? A half a win? Maybe? Que sera, right?
No. No sera!
This matters. You are right. Any one player isn't going to make and break a bench. But having those types of players, the ones that you have to caveat by saying "it won't make or break the bench", should be the end result of a off-season of trying very hard to get better. It should not be because you try to sign guys to what you consider fair-market deals for your team and then get outbid consistently. It should not be because you'd have to eat some dollars on players that shouldn't be around. It should not be because your hubris makes you believe your own players are better than they are showing themselves to be. It should not be because you aren't really trying at all because you'd rather not spend money on a very slight improvement.
One player doesn't matter, but a good bench as a whole can be a couple wins better than a bad bench, a good back of the pen a win better than a bad one. Three wins can be the difference between the playoffs and sitting at home, or the wild card game and an actual series. You can dismiss individual missed deals as you like but when the season starts, the sum of those missed deals isn't somewhere nebulous. It's sitting right there on your bench.
Of course I'm not saying this kills the team. It doesn't. First and foremost, the Nats, like all teams, wish for health. If that happens the bench's minimal impact grows even smaller. And there are always in season moves that can be made. But I want, when I talk about the Nats bench, to be able to finish the sentence "Well, I hope that the Nats are healthy... " with a "but if not, the bench should be able to handle some playing time" rather than a "because if not, they're screwed".