This will be a flawed answer as any to the dilemma, but I think it's not about the "size", but about it being a personal self-sacrifice, not a majority killing a minority because it's the most convenient thing. Spock didn't push Scotty or McCoy into the warp core, he went himself!
In this case some might argue it was self-sacrifice, the boy knew that it wouldn't be good for him, but... he's also just a boy. Smart as he may be, he was selected for this role before he could really understand it, and everything they taught him was that it was what he had to do, so how much chance had he really to come to any different conclusion, how free was his choice?
(So, I think this really is a credit to the brilliance of this show. To me, this episode ... to date ... perfectly encapsulates how SNW take the spirit of TOS and extends it in new ways.
At a fundamental level, the basic premise behind the episode is similar to classic TOS high concept episodes (or some TNG episodes)- think, for example, of A Taste of Armageddon. If that doesn't ring a bell, it's the one where two warring planets "solve" the problem of war by just having computers run the simulations and have people report to execution booths.
At its most simple, this episode is also a high concept premise done in a single episode- when is it acceptable to sacrifice a person for the good of the many? It's something that is difficult, and deeply resonant in terms of moral reasoning, made more difficult by some of the facts- the sacrifice is of a single person and provably makes the society a utopia; but it is also of a child who cannot consent, and as pointed out ... it's not painless .... it's pain the entire time.
But what really elevates the episode is the modern touches. There is obvious- the continued incorporation of strong "B plots (such as the Uhuru security training in the episode and the Doctor's daughter in the transporter buffer), but more importantly, the reliance on what we have learned in the past to deepen the meaning of the episode.
Here, the central dynamic is between Alora and Pike. We know (from the first episode) that Pike is familiar with the Netflix and Chill to get his FWB time. But this is clearly different. As we learn during the episode, they met when they were younger when Alora was on a mission to try and learn ways to not have to do the child sacrifice. In addition, her planet turned down Federation membership- at first, I thought that it might be because the Federation would require them to stop, but then I remembered the Federation allows member worlds some pretty specific cultural practices .... combine the two (along with the rebels) and you know that at least among the elite of the planet, there is a feeling of shame- a knowledge that this is wrong, or at least not right.
Which explains her actions at the end. WHY SHOW PIKE THE CEREMONY? Because she loved him, and she wanted to be seen. When they first met, she was still idealistic and looking for a solution- that's why she was there needing to be rescued the first time. She didn't want to hide this from him- she wanted him to see and understand why she sacrificed those earlier ideals. And his utter rejection (including teleporting out) led to her tears- a reminder of
what she had sacrificed as she had grown older for her sense of duty.
Meanwhile, Pike is left both realizing that he had allowed his feelings for Alora to overcome his natural skepticism, which led to the tragedy. And that while the circumstances were different, his dogmatic insistence on his sacrifice was the same rationale he just heard parroted back to him. And, in a certain way, his ideals and sense of duty had led to him being alone, staring out into space.
Both of them left realizing that they cannot recapture that past, and questioning how they came to the place they are at. Just a well-done and devastating ending that adds additional emotional resonance to a well-done high concept episode.)
