What I think you're not paying enough attention to with this post is how much immediate prospect upside the Twins have on the positional side of things and how little immediate prospect upside they have in the rotation.
Losing Arraez hurts because he's a good player. But he's also a LHB that's limited defensively. He's kind of a bad fit at first base while Kirilloff is a natural fit. You can probably strap a big mitt on Trevor Larnach's right hand and he can figure it out, too. And the team still has Matt Wallner waiting in the wings and Royce Lewis a couple of months behind him. Perhaps by mid-season we're talking about Lee and/or Julien, too.
I just listed a bunch of players.
Now if you look to pitching, you have Woods Richardson. Winder. Sands. They're all interesting prospects but none of them profile to be a difference-making arm, especially fresh out of the minors. They're at least one - and probably two - steps below Lewis, Larnach, and Kirilloff and more of an equivalent of Wallner.
That's why the Twins traded Arraez for a pitcher.