You're missing the point. He's not (and I'm not) saying that there isn't a story at all. You're right in saying that Sarkhan has a story, I wouldn't ever debate that. It's that there isn't a huge, interconnected story from block to block like they're doing now with the Origins 5.
EX: Sarkhan debuts in Alara, shows up in Zendikar. Zendikar concludes and he is MIA until Khans. A whole lot of story that has nothing to do with him happens from Scars block to Theros block. Then Khans happens, involving him greatly. Now he is MIA after Khans concludes.
However, look at how they're doing it with the Origins 5 now since Origins happened.
EX: The story preceding Battle for Zendikar brings the Gatewatch together. 4/4 members are there. Jace goes to Innistrad directly following those events, 1/4 is there, but the story still connects back to the Gatewatch this way. Things happen here, the other 3 members of the Gatewatch come in to help, and a new member is added. Next we'll follow Chandra (and others possibly) to Kaladesh. 1/5 (at least) of the Gatewatch are involved, the story is still connected.
It's a more deliberately connected style of storytelling that they're employing now, where the central cast of characters will always be at the center of the story, even if it's just one of them. Who knows how long they'll do it this way? But it's definitely different than how they were doing it.