Sure but that doesn't mean people can't disagree with it.
A-list is kinda open to interpretation... and is somewhat dependant on who is talking about it.
Indeed it's open to interpretation. I still think overall that Fassbender isn't A-list yet, he's still very new on the scene and as much as he's hanging out with the right crowd (Brad Pitt, etc), he's still B+ at best, even if he's a the top of casting directors list lately, a project won't automatically get green lighted just because of his name on it. TYAS got the green light because A-list Brad Pitt put his money and time on it.
Fassbender is the new flavour of the moment yes, but generating Oscar buzz doesn't mean anything, lots of actors generated buzz and the hype died just as fast. Movies goers may know his name, but he isn't a movie star as of yet, he is still considered an actor i.e. praised by peers and critics for his craft (and hope it keeps going so). Movie stars are Will Smith, Tom Cruise, Robert Downey Jr to name a few. They all carry a film by themselves and the masses follow during their promo tour; when Fassbender will do the same with carrying a movie of his own, and by that it means box office success and not just charismatic on the big screen, yes A-list shall open its arms to him. Shame was an indie, it didn't draw much bo success, albeit it garnered him accolades. Lots of films have little or moderate success but performance praised. In XMFC he shares the top bill with McAvoy and other big names such as Jennifer Lawrence (the new A-list girl of the moment), 2 Oscar nominee veteran McKellen etc. The Counselor, was an all-star cast with Cruz, Diaz, Pitt, Bardem etc.
Another example would be World War Z, a mess fest to me, but because it has the name Brad Pitt on it, the crowd followed, and it was successful. They should have called it "A Zombie Movie with Brad Pitt"...
Now when Fassbender lands an Oscar nod, the ultimate prestigious recognition no matter how much I loathe its political aspect, and if he is a success at the box office on his own, studios banging at his door non stop to have him in every film, add to that he is talented etc. Then A-list!