"Give app X direct access to the camera, microphone, and all my photos literally any time it pleases" and "use this camera app I trust instead" are very, very different desires.

Usually I hate the in-app cameras, because they're not optimized for my device. They're usually slower, have no flash control, no zoom, no manual exposure options, etc. I'd almost always prefer to use a dedicated camera app instead.

Because of this permissions decision, if an app wants to bake in a camera thing (nearly every app that might ever touch the camera does, even if e.g. only for a QR code reader or something), I can no longer choose. The app can't open my camera app when it makes sense.

You are missing the point, which is that you can bypass the permission system completely by directly launching the camera intent.