The mystery method is not out of date.
There is just this new trend, called "direct game" and "natural game".
I get the feeling sometimes that people get ashamed on their pua stuff, so the thing what they do is putting a complete emphasize on inner game and letting the outer game be the result of it.
Typical quotes of "natural game" lovers are: "don't think too much, just do it", "don't think too long about openers. it's not about what you say, but how you say it", etc.
People who like doing direct game, are more into passion and sexuality. They want to make out with a hot girl and fuck her, without having to use hours of routines on her. They're the kind of lazy guys, however, i do respect them because you need balls for it and i love passion and sexuality

.
This is why people sometimes say that MM, more or less indirect game, is out of date. also, a lot of people in the community found out that a lot of openers and negs don't work always, and that they're seen as unnatural and jerks.
Again, i think i've red somewhere that MM was designed for drunken party girls. i'm not a huge fan of using MM outside clubs, because there people have less bitch shields etc. and you have to use more natural game.
I'd say that you should use the method which works best for you. personally, i use the three of them equally much, depending on the situation and the girl.