Dogfooding doesn't mean you know how to build it. Take for example the graphics engineers on Unreal Engine. They almost certainly know how to fly around test zones or make stress scenarios, but they aren't going to be building large, detailed, open world maps like will be seen in the next Cyberpunk or whatever. And it's not reasonable to expect that of them, either.
Nor are the people doing UI work in Blender going to be able to make Big Bunny.
Nor are the people working on fusion360's parametric system going to build complex mechanical-fluid simulation scenarios.
Flutter is simpler than those, sure, but even in that world you have people that do nothing but fonts & text for their entire careers. They'll know how to do text stuff in flutter, but they'd be lost if you demanded they make a tiktok clone.
Nor are the people doing UI work in Blender going to be able to make Big Bunny.
Nor are the people working on fusion360's parametric system going to build complex mechanical-fluid simulation scenarios.
Flutter is simpler than those, sure, but even in that world you have people that do nothing but fonts & text for their entire careers. They'll know how to do text stuff in flutter, but they'd be lost if you demanded they make a tiktok clone.