Luis Arraez should be in the starting lineup almost every game. Looking at his career stats, Arraez has a great OBP against left handed as well as right handed pitchers. His BA is higher against right handers but he draws walks more than twice as often against left handers. Arraez career OBP against RHP is .380, against LHP is .363. Looking at the Twins roster, over the course of this season it can be expected that Arraez' OBP will be the highest on the Twins.
The Twins need runners on base for their other batters to get RBIs. Arraez gets on base better more often than any other Twin. Obviously he has earned a starting role, he was a regular starter in 2019, 2020, and 2021 (except when he was injured).
Luis Arraez should be in the starting lineup as the DH when he is not starting at another position. Arraez appears to be an average defensive player according to advanced defensive stats available. He is still a young player and can improve defensively, 1st Base could be the ideal defensive position for him.
Without a man on base a hitter cannot get an RBI. Arraez gets on base better than any other Twin. With Arraez on the bench the Twins score significantly fewer runs. He should be batting 1st, 2nd, or 3rd in the batting order.