You actually can use Stremio on iOS devices just fine. After you set it up using this guide just go to web.stremio.com on your iOS device, log in, and add that shortcut to your home page. You’ll also need to install VLC (for free) or Outplayer (I think it was $10, but worth every penny) and there’s really no way that I can tell that it isn’t a native app from the App Store.
Why not? You’re only sourcing things from real-debrid. That’s sort of one of their big selling points, is it’s not P2P, so you don’t need a VPN.