Losing Arraez is, of course, a really big bummer. Hearing about what he's like as a teammate and his approach to hitting is really, really incredible. BUT, the rest of his on-field metrics are difficult to look at, and I can't imagine it necessarily felt good to trade him.
Sure, Lopez isn't an ace, but Arraez wasn't an MVP either. Looking at what the starting pitching rotation will be this year versus last? My god, it isn't even close. Better to have five "number three" starters than two of them plus whatever one considers Archer and Bundy.
Judging by the reaction by both Twins and Marlins fans (both fanbases clearly not all that stoked), this seems to have been a relatively fair trade, if not slightly better for the Twins.