Yes, and that is a bug that has blocked enormous improvements in Firefox's speed, stability, security, and fundamental architecture for years. This is going to be a painful transition, but I'm confident that the cure is better than the disease, and that the long-term cost to extensibility will be less than predicted.
Maybe I'm wrong, but this feels similar to how the Web itself lost many capabilities and existing projects with the move away from native plugins. We no longer have Java or Flash to circumvent limitations in the Web platform, but in my experience, the Web managed to sufficiently narrow that gap so that I don't miss them at all. I certainly wouldn't turn back the clock, given the chance.
You can't even grant a website access to a specific directory. like "myimages/flickr.com" or whatever.
Stdio. It's so fundamental. And the web can't do it. After so many years. Addons can do that. But not webextensions.
So what you call a bug that needs to be removed I call basic interoperability.
But that's the problem. Things not "on your list" will simply not be possible. Right now an addon - with enough grease - can do anything that C code in the browser itself could.
In other words, the new API will cause a non-zero amount of existing addon features to cease existing and currently-possible future addons from never coming into existence.