Maybe ChiBob will chime in on "The Irishman".
The title tells what the story is about, a character study of a man who leads an empty life and an ungodly life. He made a number of wrong turns. He was too obedient to men in positions above him in power and money. He couldn't see beyond the material (or nature) until it was too late. The spirit was beyond him. This is not to judge him, as he is one of God's creatures too. He's a mirror or a sign held up to any of us in our own lives. This is the strength of the movie, and it's why his relationship with his daughter is not an isolated sub-theme. That aspect of the movie plays into the general theme of finding a meaning to one's life. Every now and then, we learn the fate of a gangster, usually a life cut short by execution. This illustrates the same theme.
Hoffa, by contrast, knows very clearly that he cannot allow the pension fund to be looted and there can be no in between position, and he lays his life on the line. This is despite his mistaken belief that he has enough goods on the mafia figures to prevent them from killing him. Even with that, he stands for something. Even if he views the union as HIS and is far from a saint in that respect, it's still something for the members and at the same time something he built or helped build.
We are supposed to think of him as courageous, even when his life is cut off, as opposed to the desolation experienced by the Irishman. We are not supposed to root for Hoffa to have buckled under in order to preserve his life. Hence the Hoffa story and character become integral to the main theme.
This is very much a religious movie in the sense of posing a religious-philosophical question or two.
In this movie, Scorsese deglorifies mobsters. This contrasts sharply with Casino and Goodfellas. Let those who evaluate his entire body of work figure out his own personal journey with his Catholic religion. I can say only that I felt that here he had noticeably altered his evaluation of the mob life, taking a much more negative take on it. It was as if he had matured finally and started to evaluate his own life and body of work. How had he managed his talents?