Whether Bartlet turned out to be as peripheral as he was originally intended is utterly beside my point that, from a story-telling perspective, The West Wing that we got was overall more about Josh Lyman than Jed Bartlet.
But I don't agree that it was. Josh as the overwhelming lead character? Not in the show I watched. Maybe if you count the post-Sorkin years, the seasons after Sam (the original intended lead character) left and Bartlet was played down in favor of Santos and Vinick, then you could perhaps make the case that Josh was cumulatively
the most consistently featured character over the full 7 years, because he ended up as Santos's campaign manager. But that's really rather an unfair standard, like claiming that Rembrandt Brown was the main character throughout all of Sliders
just because he was the only original cast member who didn't get written out in later seasons, or that Worf and O'Brien were the central characters of the Trek franchise because they were the only ones to be featured in more than seven seasons. If you look specifically at the four Sorkin-run seasons (and maybe season 5, but that sucked and I prefer to ignore it), before all the cast and format changes, I'd say that Bartlet ended up being at least as central as Sam, Josh, Leo, CJ, and Toby.
To move TNG along the slider further away from TOS and even closer to The West Wing, what was needed was to have "Lower Decks" be the norm rather than the one-off exception.
That's a very poor analogy, because a "Lower Decks" version of The West Wing
would've been a show about Charlie and Donna and Mrs. Landingham and Margaret and Carol. The main WW characters like Leo, Josh, CJ, Toby, and Sam were the senior staff, the department heads, just as the main TNG characters were the senior staff. I mean, sure, realistically it would've been the cabinet and the national security advisor and such that was the President's senior advisors and policymakers, but the way the show was written, it was the main characters who were Bartlet's inner circle.
Sure, TWW had a large ensemble including many characters out of the senior staff, but that made it basically like DS9. It's kind of the nature of TV writing that even if you nominally focus on "minor" supporting staff, they'll end up being the ones who make most of the important choices -- like Nog and Rom and Garak becoming major participants in the decision-making or serving as Defiant
bridge personnel in later seasons of DS9. So something like "Lower Decks" can't really work on a continuing basis. Even if the characters are nominally subordinates, just by virtue of being the series leads they'd end up being the chief decision-makers.