Fiction is never really about need, since it's recreational. It's about choices. And this is following the MCU's established pattern -- start out with distinct stories about separate characters, give them their solo stories, then build up to a big crossover at the climax. They did it with the Avengers, Netflix did it with the Defenders, and now we get it with the, uhh, Whatiffers.
I agree it's rather formulaic, but the best thing about it is that it's an opportunity to actually tell a story about Uatu rather than just having him be the narrator. In the comics, Uatu was already a familiar character from The Fantastic Four and elsewhere by the time he became the host of What If...? But here, we met him for the first time, so if they hadn't done a story like this, he never would've had a chance to grow beyond just being Rod Serling.
And the other interesting thing about how they did it was that in the Fantastic Four comic; The most taboo thing Uatu, The Watcher did to intervene in a situation was to appear to the group, and pass along knowledge they didn't have. In the actual comics continuity he first appeared in FF issue #13 when the FF decided to finally complete their aborted trip to the moon to check out the mysterious "Blue Area" which turned out to be an abandoned ancient alien city, where Uatu resided, conducted research and observed humanity. Uatu technically wasn't breaking his society's taboo because both the FF and the red ghost had invaded his home, and he was allowed to defend himself / repel intruders.
The next time Uatu appeared,, was FF issue #48, and that was the first time he broke his society's rules by attempting to hide the earth from being detected (surrounding it with a large group of fake asteroids), andappearing to the FF and warning them that the herald of Galactus - the Silver Surfer - was heading towards Earth; and if he signaled his Master, Earth was doomed. In the end he went even further by helping the Human Torch travel to the home of Galactus, and showed him what to retrieve to make Galactus agree to leave Earth as it was.
^^^
As an FF fan I am really hoping we get a feature film that follows a lot of the original Galactus / Silver Surfer first appearance story, including Uatu, the Watcher appearing to the FF, etc. But we'll see if the MCU even gets to that point with the FF stories it ultimately tells. But given they're actually going to do a "Celestial" storyline in the upcoming
Eternals film; and they've already introduced ego the living planet, with
Guardians of the Galaxy - yeah they should also bring in Galactus In all his purple and blue armored glory.
But yeah the above is just to illustrate one thing I did enjoy about the previous
What If episode; and that's the fact that Uatu can and actually will fight. I don't know if they've done the stories with him like what we saw on this episode of What If; but during my time of reading Marvel comics, they never depicted Uatu or any other member of his race actually engaging in combat; so that was both interesting, surprising and fun to this old Marvel comics fan.