I was analyzing variations after
1.e4 Nc6 2.d4 d5 the other day. All of the following lines seem to score well for Black and lead to pretty comfortable positions:
[FEN ""] 1. e4 Nc6 2. d4 d5 3. e5 (3. exd5 Qxd5 4. Nf3 (4. Be3 e5 )4... Bg4 5. Be2 O-O-O 6. Nc3 Qa5 )3... Bf5 4. c3 f6 5. f4 (5. Nf3 fxe5 6. dxe5 e6 7. Bb5 Bc5 8. O-O Ne7 )5... Nh6 6. Nf3 e6 7. Bd3 Be7 8. O-O O-O (8... Qd7) 9. h3 Qe8 *
You could argue that, in the mainline above, Black's knight is misplaced because it isn't really targeting anything and it's blocking his c-pawn, which is a nuisance because c5 is Black's main pawn break in the French pawn structure. But on the flipside, he's managed to develop his light-squared bishop outside the pawn chain, and he still has the f6 break at his disposal. So if you compare this to the French, as far as I can see it's just a matter of "bad knight" vs "bad bishop"; I don't see why one opening should necessarily be considered better than the other.
So, what are the reasons that
1.e4 Nc6 2.d4 d5 is considered a second-rate defense and not used at the top level?