Is Rosario really rated the worst defensive OF in baseball?
According to this metric, yes (and it isn’t even close). Out of all outfielders, Buxton finished 5th despite missing all that time, Kepler 16th, and Rosario 92nd out of 92. Twins OF combined for 22nd in the league despite having two of the top 16 outfielders.
As for the Twins infield (out of 218 players):
Donaldson 18th
Marwin 19th
Sano 194th
Arraez 206th
Polanco ties for 217th
https://baseballsavant.mlb.com/leaderboard/outfield_outs_above_average?type=player&year=2019&min=q