Electric superman was in continuity so it was the character in the 'proper' timeline and while Red son wasn't the proper superman, superman adventures was and it didn't hinder Millar's ability to write the character.
You don't need to be the best writer to handle the character, Greg pak is an excellent writer but not amongst the most celebrated and many would argue that his superman was the best out of the N52 era.
Alan Moore, Scott Snyder, Mark Waid, Jeph Loeb and Joe Kelley all wrote superman at very high power levels and didn't need to resort to killing the character to tell their stories.
So, what makes Superman more difficult to write for is the combination of his immense power and immense morality. This is the classic/iconic/traditional "proper" Superman. There are versions of Superman in continuity that do not present these problems, such as Clark Kent aged 16, Superman Blue, Superman One Million, and so on. Those aren't the characters that people have trouble writing unique and interesting stories for or feel are overpowered or boring.
Going through your list, it's really interesting to see how these expert writers have handled this challenge:
Alan Moore didn't literally kill him, but he definitely told an ending story, like All-Star, and used a truly omnipotent being as the foe.
Mark Waid wrote an origin story, as Clark is developing into the iconic Superman.
Jeph Loeb decided that "I didn't feel comfortable being inside the head of an icon." and so told the story of Superman from the perspective of others, essentially making Superman the setting. This is the path I tend to favor, and seems the most sustainable.
Greg Pak, while not quite being the Who's Who of comicdom definitely made a character who was ousted in favor of the return of a more "proper" Superman. He chose to make him interesting by changing his morality, as well as giving him a power that forfeits his powers, not unlike Superman Blue.
Of the guys you listed, I think Joe Kelley is the only one who wrote a proper Superman and who isn't on the "Who's Who" of Comic writers. Incidentally, he also didn't choose to write an origin or endpoint story. He chose to handle the character by changing the setting, which, honestly is kind of brilliant. First Metropolis changed with the Y2K virus, which allows them to re-do the kind of introduction to Metropolis story types, then a new kind of Kryptonite - a virus! allowing you to do a fresh Kryptonite story, then a truly omnipotent antagonist in Emperor Joker, then President Lex changes the setting fundamentally again, then they Return to Krypton, changing the setting again, then Our Worlds at War as a big crossover even before dipping back into boring Superman stories that re-emphasize why people feel this way about the character. They tried to do a journey into the body thing, but that's not Superman, it doesn't fly, so to speak. And even this whole experiment goes to show that there are only a handful of Superman stories, and because of the nature of Superman, only a handful of ways to tell them. Case in point, you can give Batman any number of viruses and he still be Batman. Even Batman with a cold adds an interesting wrinkle to the story that's very different than if you gave him, I dunno, HIV. Superman? You really can only give him a Kryptonite virus, regardless of the symptoms, the scale of his abilities make grounding his problems simply more challenging and less sustainable.
Now, STAS and associated comics does bring up an interesting wrinkle to my theory. I'll consider that at length.