True, if you assemble an elite production squad, there is nothing to stop all 13 episodes from being great, but I'm trying to be realistic.
I also disagree that either DD or JJ have really suceeded in doing this. Daredevil season 2 has a big three episode lull in the middle and peaks before the it's even halfway along. Season 1 gets close enough, but still could have used some trimming, especially the finale episode. JJ was even worse than season 2 of Daredevil. But in that case it may have suffered from being a little TOO intested in it's own world. There was a whole episode or two where all that happened is Simpson got high on some combat drug that came out of nowhere, and also the scene where Jessica is literally overpowered by the Kilgrave support group (wtf?) and let's not forget when she's sleepwalking and gets hit by a vehicle...maybe others don't see it that way, but to me these were all very obvious signs that they only had 10 or 11 episodes written out and needed to pad things significantly to hit that magic 13.
So basically what I'm saying is that only season 1 of DD has really gotten close to making 13 epsiodes work.
But Daredevil was the original concept for Netflix, was the most popular by far of all these characters, and has a much deeper and richer lore than any of them as well...if they keep down this path I don't see myself returning after The Defenders. It just feels like a slog too often and I almost never feel like rewatching any of them already.
I think elite is a strong word. There are at least a dozen shows on Netflix alone that pull off 13 episodes quite well. And while DD definitely has a bigger gallery to draw on, LC and IF aren't exactly scratching for 13 episodes of fodder in the comics, and JJ, while new is designed to siphon from the MU at large, and to replace with original characters as needed. There's plenty of fodder and plenty of talent available for these characters to have jam packed rip roaring 13 episodes.
What strikes me as the problem is improper focus and structure. I loved Luke Cage because of the subject matter and style, but they didn't really have episodes, and that got heavy for everyone by episode 9. That's not a lack of an 'elite' team or necessary fodder for Cage's stories. There's so much from his universe that they didn't even touch on. They just had some weird focus that brought them to magic bullets that somehow didn't kill, and a brother storyline that never synced thematically with the much more interesting Club Mogul and Politics storylines. That's not the episodes, that simply a sudden shift in focus that would have been alleviated with better structure.
Likewise, DD1 didn't need to trim the finale, they simply needed to spend the time they weren't spending tying up plotlines to underline the thematic parallel and contrast of DD and Kingpin so their alley brawl wouldn't be so anti-climactic.
JJ didn't need fewer episodes, it simply, as you said, could have had less interest in the very small corner it drew itself into. A Purple Man who was more like the comics, less neutered for the sake of being only a weak abusive ex, would have opened up really twisted storylines that in the version we got were relegated to dialogue. They had the material, they just chose not to because of their focus.
I can do the same for every series. What I hope they do, instead of shortening future seasons and validating and encouraging these narrow focuses on these very large characters, I hope instead they'll find people with more expansive visions, who will dive into IF instead of ignoring Danny to deep dive into Harold Meachum (like they did Simpson, iirc), people who are interested in the power struggle between Cottonmouth and Diamondback and who gets caught in the middle and not someone who just... runs out of things to do with a villain who was second to Kingpin in terms of impact, imho. It's telling that the series that got closest to earning 13 episodes is the one that simply took the time to deeply explore its hero and its villain.
In short, I'd rather someone actually explore these characters instead of shorten their seasons so that they don't have to. Because if the issue is lack of focus and structure, then the ideal number of episodes is 0.