Here's my take, for good, bad or indifferent:
A prequel is something that I think should set up "Oh, I didn't realize" moments for the audience. Yes, I'm aware of the time and writing difference from show to show, but I'm ignoring that because the purpose of SNW is to give some life to characters we knew
next to nothing about. @Turtletrekker already posted the video of Chapel and the
4 minutes of time she had out of the 70+ episodes of TOS that gave her something to do. She did even less in the films.
So, SNW allows me to go "Oh, wow there's a lot more history to this character than just, 'I'm sad because my fiancé died and I'll stay on this ship.'" It gives some much needed context to relationships, not the least of which is why Spock hid his mind (no katra at the time) inside Chapel when Henoch commandeered his body.
Would anyone have noticed? Probably not. But, what they are doing is extremely enjoyable. It's a reminder that characters are not just born perfect whole cloth, and remain stalwart paragons of virtue until their dying day. They are supposed to be people, living, breathing, failing and learning people.