We know that the Eldrazi weren't going to win. After all, you said it, if they did, we'd never be able to stop them. And that's the end of the game I guess, because every other plane succumbs to Eldrazi until they find New Phyrexia, then every plane succumbs to Phyrexian Eldrazi.
We expect the Gatewatch to win already, so there's no tension in the actual conflict of the story. And because we already know that Wizards wants to build a super team, we know that none of the planeswalkers were going to die. Well, what's left?
I've said this in another post, but the characters on the actual plane can die any time. Hell, they can die by the thousands, millions, even and we still wouldn't care. They've died on New Phyrexia, they've died on Dominaria, in the first Phyrexian invasion, and they'll die on Zendikar. We're not being shown anything new. The plane can change dramatically by the time we leave. This has happened in literally every set we've had so far. Again, we're not being shown anything new.
So I ask again, where's the tension in the plot? Where are the surprises?