I do think they should have spent more time, but my counterargument is it should be obvious to Gohan and co. that these people have families, they have lives outside of this tournament, people they care for that are going to be erased, Gohan at least is the type of person who would be thinking that throughout the whole tournament, him having some type of hesitation would suggest that thought never occurred to him, which really messes with his character, and makes him really oblivious to the other fighters. Him seeing the locket after, and the look he gave implies he knew what he was doing, and he wishes he didn't have to be reminded of it because it makes it that much harder, but he has to move on.
It shouldn't be a huge shock to Gohan. Maybe to Goku or Vegeta who are pure saiyans who have that emotional disconnect at times, reflecting on the locket could work, I just don't think it's needed for Gohan who isn't like that.
Pure saiyans were a mistake.
All hail our lord and savior the hybrid saiyans.
And that person has 3 eyes.