White finds it very hard to make any progress without liquidating the pawn structure, which erases the good bishop advantage.
Why play the winawer?

Black does the same thing in the Nimzo-Indian and Ragozin defenses, two of THE best ways for Black to play against 1. d4. White does something similar in the Rossolimo Sicilian. Essentially, a bishop may be slightly better than a knight, but if you can get compensation such as a weak king or pawn structure, then it’s completely fine and often the best choice.

Also, once you've played c5, there's no good way to hang on to the bishop. After 5.a3 Ba5 6.b4 cxb4 7.Nb5, the knight is threatening the annoying Nd6+. The discovered check, 7...b3+ 8.c3 doesn't do much. The line is playable, but it's a real uphill battle for black.

Black does the same thing in the Nimzo-Indian and Ragozin defenses, two of THE best ways for Black to play against 1. d4. White does something similar in the Rossolimo Sicilian. Essentially, a bishop may be slightly better than a knight, but if you can get compensation such as a weak king or pawn structure, then it’s completely fine and often the best choice.
Fair point. However, often, the bishop goes to b6 in the other ones, especially the nimzo, but I should have thought of that. If its ok in those other openings (trading off the "good" bishop for imbalances), why wouldnt it be good in the winawer? Thanks.

Also, once you've played c5, there's no good way to hang on to the bishop. After 5.a3 Ba5 6.b4 cxb4 7.Nb5, the knight is threatening the annoying Nd6+. The discovered check, 7...b3+ 8.c3 doesn't do much. The line is playable, but it's a real uphill battle for black.
Black should play 6...cxd4, not 6...cxb4. If White takes the Bishop, you get the Knight. White should not capture the Bishop.

Also, once you've played c5, there's no good way to hang on to the bishop. After 5.a3 Ba5 6.b4 cxb4 7.Nb5, the knight is threatening the annoying Nd6+. The discovered check, 7...b3+ 8.c3 doesn't do much. The line is playable, but it's a real uphill battle for black.
Black should play 6...cxd4, not 6...cxb4. If White takes the Bishop, you get the Knight. White should not capture the Bishop.
Agreed. But my point was "there's no good way to hang on to the bishop". The OP is asking why, in the Winawer, trade the good bishop for the knight. What I'm saying is, once you've gone 4...c5 (or Ne7) after 5.a3, you're pretty much going to have to give up the bishop anyway. Black can try 4...b6, and if 5.a3, retreat the bishop to f8. I think the jury is still out on this line....

General principles are all well and good, but ultimately chess is a concrete game, and the winawer just kinda "works." A lot of its lines are insane, but black is ultimately fine in all of them.

It's complicated. Black's compensation comes from the bad pawn structure. White gets attacking prospects early on in the game, but black is somehow fine in all the lines if he knows enough theory.

It's complicated. Black's compensation comes from the bad pawn structure. White gets attacking prospects early on in the game, but black is somehow fine in all the lines if he knows enough theory.
Had a friend go through 22 moves of winawer theory as white against a NM, prepared a novelty, where black was fine if he sacrificed an exchange. He played that line, 3 moves later, my friend (2100) lost. Blamed it on the opening (not knowing enough theory)
anyways I learned not to play the winawer for either side if I valued my life.
'The defense is anti-positional and weakens the K-side' - Fischer
https://www.chessgames.com/perl/chessgame?gid=1044346

'The defense is anti-positional and weakens the K-side' - Fischer
I see your win and raise you one!
Fischer's comments were utter trash. Fischer actually had more trouble against the French than any other opening.
Still to this day, my favorite game of all time:
https://www.chessgames.com/perl/chessgame?gid=1044135
Move 30 by Black is just absolutely nasty!
Eh, beats running away with the knight from nf6 giving white the advanced pawn with no tempo loss. Still, Potayto, potatoh.
@16
"Fischer actually had more trouble against the French than any other opening."
++ Larsen must have thought the same...

Also, once you've played c5, there's no good way to hang on to the bishop. After 5.a3 Ba5 6.b4 cxb4 7.Nb5, the knight is threatening the annoying Nd6+. The discovered check, 7...b3+ 8.c3 doesn't do much. The line is playable, but it's a real uphill battle for black.

I just don't understand why you would trade the GOOD bishop for the knight.
black gets an unbreakable fortress on the queenside which allows him to fight for a win/draw

I'm not sure what your point is. The line you've shown, with 8.Qxg7, is known to be inferior. Better is 8.bxa5 dxc3 9.Qxg7 Rg8 10.Qxh7, and white has a slight edge. Smyslov clobbered Botvinnik with this line all the way back in 1954 in their World Championship match.
https://www.chess.com/games/view/64753
I'm not saying white has a huge advantage. I'm just saying, again, if you want to play the Winawer, be prepared to give up your DSB. In most cases, you'll get a better game than trying to hang on to it. If you want to keep that bishop, just go 3...Nf6 and follow up with Be7. Interesting is the Morozevich variation, 3...Nf6 4.Bg5 dxe4 5.Nxe4 Be7 6.Bxf6 gxf6.
I just don't understand why you would trade the GOOD bishop for the knight.