Yeah problem with the video is it highlights the core issue with Luke’s characterization and development throughout the ST, Ben’s characterization.
Luke goes through hell because of one instance: his instinctual decision to strike down Ben in his sleep. This results in his depression, redemption from a talk with Yoda, then finally confronting Ben to try to bring him back.
Makes sense if Ben in the ST was Darth Caedus (Han and Leia’s son who was exceptionally intelligent and talented in the force but flirts too much with the dark side and is lost forever). Darth Caedus is irredeemable despite the best attempts by Luke and his extended family, Caedus causing irreparable harm such as killing Mara Jade. However, even causing far more destruction than Kylo ever did, Luke is sworn to redeem Jacen and it becomes up to Jaina Solo to take down her brother once and for all. Jacen does redeem himself but it is too late as his sister ends his life.
Unfortunately, Ben is far from the capable powerful mastermind Darth Caedus was. He is still a Sith fledgling that has so much light in him that Snoke specifically instructs him to commit more brutal acts, hence why Ben killed Han Solo. There is so much good in him that Ben couldn’t shoot the resistance ship because he sensed his mom was on board. Hell, even Rey senses the good in him and goes to Snoke because she believes he can be redeemed, mirroring what Luke did for Vader (real original).
You are telling me that Luke whose character is honestly sensing the good in people to a fault (see Vader for movies, Mara Jade for non canon) and a typical Jedi trait of giving bad guys the benefit of the doubt (see Obi Wan and Ventress, Maul) failed and refused to see the good in Ben when nearly everyone else did?
Essentially, this depressed turned his back on the force Luke can exist but he cannot exist with a Kylo Ren who is stuck between good and evil. He must exist alongside a Kylo Ren who is so soaked in the dark side and destruction that he makes Palpatine look like Nute Gunray.