It’s actually a lesser mistake, considering the first time he tried to save one of his genocidal relatives he kicked the hell out of him and then cut his hand off before just barely managing to stop himself from delivering the killing blow.
This never tracked with me, I think it conflates wildly different circumstances, a young Luke already being hunted in active combat is not the same to me as an old Luke reading the thoughts of his sleeping nephew. I was fine with the backstory of how Luke failed Ben being ambiguous and I wish it stayed that way, when the truth is revealed it still for me feels so abrupt and Luke seems barely nudged into going 0-100, again it’s not that I hate Luke failing thematically or turning away from the force but the ultimate written explanation is where I just can’t make that leap.