For me it is similar to having the PT end with Anakin the hero, and then introduce him as Darth Vader in the next movie, and then show a tiny flashback to explain how Anakin is suddenly an evil mass murderer.
Additionally to know that Anakin fell to the dark side is supposed to be a shock to the audience, and a disturbing one at that. To know that Luke gave up is at first shown to be sympathetic, then unforgivable, then just blase when the previous two flashbacks become synthesized. But ultimately we’re meant to think it’s a sensible turn of events when not only is it not but it’s hardly fleshed out enough to empathize with either Luke or Ben’s situation. Obi-Wan’s apathy to Vader is at least justified by Vader explaining that Obi-Wan wanted Vader to redeem himself up until the desire to see him be redeemed could no longer be sustained.