it's kind of hard to defend a 'method acting' criticism leveled at a period film...because the sort of training and research an actor undergoes to play an historical character is part of an approach   that cannot, as a result, be fully dedicated to 'method' techniques...learning fight choreography to play a role is but one    factor which forces one to redefine this criticism. Same goes for learning how to move in period costuming, or learning a different dialect than what one speaks normally (all of which Mortensen did for this role).
Like I said, most people who think they know what method acting is don't actually know what they mean. It means quite simply preparing for a role by incorporating one's own emotional experiences into creating a character's responses. This is standard for any actor's approachh to performance. If it isn't, they're not doing their job, not good actors, or both.
the "method" is but one approach, and it is a very standard and effective acting model taught to virtually anyone who studies acting or directing   after   the 1950s. Not incorporating the principles of the 'method' technique basically would make an actor someone in the mold of melodrama or historical style...and that is clearly is not what defines the actors anyone considers "good" in this day and age.
Good acting incorporates a variety of approaches. I would hazard a guess that there is no one that anyone could refer to as a "method actor" these days with any accuracy, because EVERY actor is now trained in Stanislavski's methods....it is an idiomatic term that was fashionable for a time when this school of acting first made waves in the 1970s.