It wasn't _just_ the sandboxing. It took an unreasonably long time for MS to loosen restrictions on "sideloading" (read: distributing sandboxed apps outside of

It wasn't _just_ the sandboxing. It took an unreasonably long time for MS to loosen restrictions on "sideloading" (read: distributing sandboxed apps outside of the Microsoft Store), and the deployment story for line-of-business applications was abysmal for years. I'm not saying the AppContainer sandbox is perfect, but I suspect it would have gone over a lot better if the early distribution story for UWP had been less of a disaster.