I thought the point was that this was the way the world worked and that you couldn't get out of it. That, and the fact that good men are forced to do bad things by circumstances.
Never seen the movies but in the book Michael absolutely could have gotten out. He chose not to because his honor would not suffer the insult to his family that occurred. He might have done differently if he hadn’t been in New York when the attack happened and the discussion over retaliation was going on. He was assumed to be on the outside. Sonny was in the family business. I don’t recall if Fredo was but Michael was thinking of becoming a professor and moving far from New York and the family.
That's my understanding of the first film as well. Michael, like most tragic heroes, was brought down by his own pride. Gangster and crime stories are often better understood as forms of tragedy; Scarface and Breaking Bad are also tragedies about men brought down by pride (and, in the case of Scarface, many of the other seven deadly sins as well).
Michael is the one Vito was trying to keep clean in hopes that he'd eventually be able to rise into a position of legitimate power, outside the criminal underworld.