Ruhwedel was a positive player in the playoffs. And I think you just have completely ridiculous expectations for what a #6 defenseman is supposed to be.
You're criticizing him for him being nothing more than a guy that doesn't "hurt the team". Dude, what the hell do you expect depth players to be? A guy who doesn't "hurt the team" is basically the definition of a depth defenseman or a depth forward
I don't really give a crap enough about Ruhwedel because he's thoroughly vanilla, but if you find yourself having a problem with him being a regular because "he's not exciting enough" or "he's just not hurting the team", you really need to reconfigure your expectations for the role. The amount of #6D who actively help their team win is 0. A guy in a #6D role is literally the definition of a "don't screw up" role.
The type of defensemen who have been #6D on the most recent cup winners have been guys like JJ, Schenn, Coburn, Bortuzzo and Djoos. Expecting your #6D to be anything more than a "good god, please don't lose the game for us" is just being completely unrealistic for the role we're talking about. This isn't even me defending Ruhwedel, he's thoroughly whatever in my eyes, it's just insanity to be mad that you don't have a #6D that's winning you games because literally no one has a #6D who's winning you games.