the author is more interested in how humanity as a whole would react to his fictional scenario than he is with writing characters with depth

This was my impression as well and I think it works only because the fictional scenarios are extremely creative along with sometimes gratuitous science-fiction details from the author’s imagination. And even though most characters seemed unrealistic as people I still liked them as characters and found them memorable.

I also read (listened to) Voyagers by Ben Bova recently and while the fictional scenario was interesting, the character development leaned heavily on the relationship between the hero scientist and the promiscuous young scientist, a writing style which I found more boring.