To me, saying Doc Brown is too recognizable to be a convincing Kruge is to say Shran is too recognizable to be a convincing Weyoun.
To you, maybe. To me, I have zero idea what this means.
It means this is all the same actor, and this is all from just Trek.
And they can get away with using him that because he’s never had a role or persona that defined him to millions of people.
Horror movie fans notwithstanding. 😉