The biggest shakeup in the Marvel Cinematic Universe arguably wasn't Thanos' snap, it was Coronavirus. The global pandemic caused a shockwave through the MCU that has reordered everything. By this point we were supposed to have already seen Black Widow and the first Disney+ MCU series was going to be Falcon and the Winter Soldier last summer. Jac Schaeffer wrote the screenplay for Black Widow and while we're still waiting for that film, the latest entry in the MCU is still a product from Schaeffer, as she's also the lead writer of WandaVision. And she says that, as off-the-wall as WandaVision is, it was actually easier to write than Black Widow.
WandaVision sees two of the Avengers trapped in an ever-evolving world of television sitcoms, and the premise alone makes it the most unique thing to be done in the MCU so far. One might think that would make the show a little more difficult for a writer to figure out, but Jac Schaeffer tells SyFy Wire that she actually found it easier to approach WandaVision because she enjoyed the challenge of it. Black Widow being a more traditional superhero story seemingly didn't engage her in quite the same way. According to Schaeffer,
I like the sort of crazy pond of being 'It's a sitcom and it's the MCU." That is incredibly challenging but it's something I enjoy and it makes sense to me, the puzzle of it. I worked on [the upcoming Black Widow movie], and I found it harder to do more of a straight-ahead superhero story. It was just a little harder to hold on to, whereas the experiment that was WandaVision used every single piece of my brain and that of my writers.
It seems that Black Widow simply wasn't quite as exciting an idea to Jac Schaeffer when compared to WandaVision. While it'll make history for having a female protagonist, the story itself was far more contained than the acclaimed live-action series. That said, the fandom can't wait to see her next project within the shared universe-- especially after seeing her work on WandaVision.
While WandaVision's very different concept could have felt overly complicated, the puzzle of it all is exactly what made it so appealing, not only for Jac Schaeffer but the rest of the writing staff. It's understandable that coming up with something new for Black Widow could have been tough, especially considering how many superhero adventures came before it just in the MCU. Conversely, whatever they came up with for WandaVision was going to feel fresh and new by definition. And the fact that there was no precedent probably gave the writing team a lot more freedom than they had for something like Scarlet Johansson's solo flick. After all, there's an expectation for what that movie is going to look and feel like.