The question is how would we expect people to react when practically speaking, their entire civilisation has been wiped out?
I think alot of it would play out as shown in NuBSG, but, I don't believe everybody, all the time would be so depressing. I believe there would be lighter moments, there would be some fun and some moments of joy. Now, maybe we can say those happened off camera, but, they went overboard with the "real Grit" removing the lighter moments/fun/joy, so, the "reality pendulum" swung over to the other side and became unrealistic
exactly. In dark and depressing situations, it's even more important psychologically to have humor to relax and deal with the tension of the situation.
The show needed more moments like Tigh joking about how the crew wasn't eating paper because there was a paper shortage along with all of the other shortages.
And yeah, looking back I guess Baltar and Head Six were supposed to be providing much of the comic relief, but it wasn't enough. And even then, that was only for the early part of the show, before Head Six turned more serious.