Good teams need 8-9 starters each year. Also he provided us with 2.8 WAR last year, which was 46th overall in MLB last year (for pitchers). He finished ahead of Ryu, Bieber, Sonny Gray, Pablo Lopez and just behind Yu Darvish and Ohtani. While he may pencil in as our #5 to start the year, he may spend a portion of the year as our 3rd best starter. He may also finish the year out of the rotation.
I'm all for adding Ray or Gausman (or both if we somehow have the cash), but you can't just discount the value of depth in the rotation.