Grapes of Wrath: Do the Joads share responsibility for their situation?

Grapes of Wrath doesnt hesistate to criticize things like capitalism, corporations, land lords, etc..., which is fine. However it seems to imply that all of the Joads' problems with poverty stem from the system and that they have 0 responsibility or control over their fate, which I would disagree with.

The one question that stuck out to me while reading the book is: Why do the Joads', particularly the older ones (pa, ma, and Tom), seem to believe that the only thing there is to do in life is to go to California to work on a farm. Even after multiple people telling them that its a scam and that handbill they received is to just to get as many people coming over to drive down wages, they do not seriously question their decision and keep going to California, and once their continue searching for a farm job that will pay barely enough to eat.

The fact that they could do literally anything else, doesnt seem to cross their mind. The book never even says that for whatever reason being a farmer in California is the only viable option for them. Its just not considered. In fact the book does imply that there are other things to do, such as the tractor drivers in Oklahoma that get $3/day (2x more than what they will get in California). Al Joad does consider being a Mechanic but his family is not very supportive of him because it would break up the family.

So at least for me, the lesson I have drawn from this book isnt simply "capitalism bad" like many other criticisms of this book say, but rather that one must always be ready to think critically and to be ready to adapt, because if you dont, you will end up like the Joads.