I don't disagree but that sounds like those being influenced would be the focus of the story, not the planeswalkers.
Old Walkers could create entire worlds/planes: this makes them very hard to challenge and thus not the greatest protagonists. You could do some cool stuff in how near-unlimited power and immortality affects them but that isn't something you can make a series out of unfortunately. Protagonists have to be challenged to be compelling.
This is for mainstream appeal. I don't think WotC is interested in making high-brow storylines just yet
I mean, they already did it by making Urza both a protagonist and an antagonist simultaneously, as well as facing a "big bad" type of external threat throughout. And I think you can do it in a series. It took Urza 2 books to get over his madness (though it could easily be argued that he just moved into a different madness). How many episodes would that bring you? Just for comparison, Neil Gaiman/Terry Pratchett's book Good Omens was just made into a mini-series that was 6 1 hr episodes long. That's one book. It's totally doable to turn it into a series. And look, in those early books, Urza is a central character, but after the Brother's War stories really focused on the people around him or the people who were the result of his machinations. Those would be characters like Xantcha, Barrin, Jhoira, Karn, Rayne, Gatha, and Gerard (who then had his own surrounding cast).
This kind of thing, in my opinion, is what would make an MTG show unique in the sci-fi fantasy genre. The basis for it is already there. Almost in a West Wing sort of way, where the story is about the President and the challenges he faces, but is as equally about his staffers. But I guess in that sense, maybe the idea is too high-brow
And like we mentioned... if they're talking about it revolving around the planeswalkers, it's not going to be them in the old-style.