I do think there’s a bit of misplaced ego in him thinking a spin-off for his character would’ve been a massive hit.
Like… we all saw that backdoor pilot they made. At best, it was fine. Maybe could’ve squeezed out a season or three. But an Office-level success…?
I think there’s a very specific alchemy to making a spinoff that’s comparable to the show they’ve spun off from, and I don’t think it was on display in The Farm. For one thing, it felt like a little bit of a retcon on Dwight’s family life. For nine seasons, we were given the impression that Dwight was the most comparatively normal one in that aggressively Amish family. Suddenly we’re in the show’s final hours and here’s two fairly normal siblings that Dwight has never mentioned by name despite divulging a ton of information about the Schrutes to his coworkers and the camera crew over the years.
Now, granted, you can basically say the same about Frasier, but it just felt so much less plausible with Dwight.