While I agree that Wallner has been lousy this year, he had stretches like this last year as well and came out of it to post really good offensive numbers. He hits the ball very hard and when he squares the ball up, it goes a long way. Going back as far back as Harmon Killebrew, there's room for elite power in any lineup. The eye test has told me that Wallner has struggled in the outfield this year, but the numbers in BBRef say that he's about average, just a bit below and he undeniably has a strong arm. Wallner's straight-ahead speed is average to a bit above, so it is about routes and jumps for him as an outfielder.
Both Larnach and Wallner need to hit to be assets and an OPS+ less than 100 tells me they are hurting the team. Wallner put up two partial season with 138 or better OPS+ numbers. IMHO that justifies having patience with him. Larnach has been more consistent the last two years, but his numbers haven't exceeded average-ish in any single season including 2025. I don't think there is room for two such players on the Twins roster, but we've been there for most of this season (except for when Wallner was on the IL).