FWIW, Ruiz had the 7th highest OPS of any catcher in the MLB last year (.717) (minimum 3.1 PA per team game played). He was 8th in slugging (.409) and 5th in BA (.260).
If he's able to improve his fielding and maintain, or even improve his hitting, he's a potential all-star. If he can't improve his fielding, he'd be a fine (and cheap) DH assuming Milas is able to grow into the starting role. There is no way Ruiz, if he continues to hit, will be a backup catcher.
As a reminder, he's only 25.