Titanic was based on a real life event, so hiding the fact that the ship sinks would be pointless. Avatar didn't have anything deep to hide so they didn't bother and The Phantom Menace was a prequel.
By what standard are you judging "can't do anything right"?Well maybe MCU Peter interpreted that to mean, "I must be even more self-destructive and a bigger f--k up than MCU Tony was, and boy will I f--k the place up." It's logical when you choose Tony Stark as mentor, put him on a pedestal, never have the character acknowledge the stuff MCU Tony actually does.
The emphasis on Peter being flawed and so on which in the comics usually means he would act based on what seems reasonable and plausible in front of him and come to wrong conclusions (which you see in the first Raimi where "Don't tell Harry" and Keep MJ away are obvious mistakes but you understand why he's making these choices) in the MCU leads to a version who seems incapable of doing anything right. This has been a tendency since the BND era as well.
It's obvious to both Peter and Octavius that the latter will not survive what he is about to do. There is nothing that Peter can do to stop him and blaming it all on Peter removes Octavius's agency in this situation. All he did was ask Octavius how to stop the machine, he didn't tell him to die trying to stop it.And it's odd that Peter let him and doesn't stop to think about Ock dying or his body not turning up afterwards. It's one of those things which 616 Peter in general, wouldn't let someone else do for him, or at the very least walk away without confirming he'd be alive.
The no-kill rule itself was never truly believed in or thought through. It was created to avoid parents protesting violence in superhero comics and these days it largely exists to justify keeping villains alive because the stories won't end.Let's face it, movies are cheats they obviously never believed the "no-kill rule" and thought things through.