I think it reflects poorly on Luke's character that he could simply see the bodies of the two people who have raised him from birth brutally murdered and not even an attempt at burial
We have no idea from the film whether Luke buried his aunt and uncle or not. The scene shifts to the Death Star right after Luke finds their bodies in one of the most dramatic transitions in the film. We can only speculate that it probably would have been unsafe to hang around too long at the Lars residence. Luke was lucky not to have gotten picked off or arrested just coming back to make sure they were OK.
Okay, that last part does sound logical. But the real problem is that we are not shown that the two deaths have had any impact at all on Luke's life. He goes on like they're forgotten almost immediately.
I don't assume stuff in movies/TV. If I don't see it or hear it or it is not pointedly implied visually or audibly, I assume it didn't happen. But we are beng asked to conclude that Luke does care for these people but neither he or the movie shows that to us. One little line of dialogue could have done it. Just a mention of them by Luke followed by a gaze off into a bulkhead or something would have said a lot. I was always left wondering if he cared for these people.
We know Luke cared for Owen and Beru, because he rushed into danger -against Ben's plea - to make sure they were OK. He had a look of horror and outrage when he saw their bodies. The transition to the Death Star is one of the most dramatic in the film, mainly due to the music. When Luke comes back to the sandcrawler, he doesn't even speak at first. Ben's way of speaking to Luke about what would have happened had he been there had the tone of consoling him. Those are all cues that Luke cared and was emotionally affected by what had just occurred.
Is it explicit? No. It's implicit. It's time for the story to move along and for Luke to get swept up in the adventure.
Would it be better if it had been explicit? Well, I hate to say it, but in Lucas's hands (which the 1977 film was), not necessarily.
In The Phantom Menace,
I personally found Anakin's admission that he misses his mother to be one of many highly cringeworthy moments in the film. For one thing, it was Padmé who finished Anakin's thought for him. It wasn't even a straight up admission; it had to play like he and Padmé were already soul-mates. (Maybe Annie was just going to say that he missed the two suns in the sky. He did keep complaining that he was cold. Sir.
That criticism aside, and in all seriousness, sometimes things are just better when you have to read between the lines. I guess in this case, it's up to the audience to decide whether it really works or not. It did for me; I guess it didn't for some people. That's cool.