There's no mafia story in this movie and the plot is very weak, focusing on irrelevant characters for too long but failling to create any connection to these characters.
We have a bunch of mafia guys with no actual enemies. A mistress we don't really care about, since the lead character doesn't seem to really. A "business associate" turned rival that only Dickie really interacts with and in the end doesn't seem relevant to anything.
The Sopranos connection is weak at best, except for the Junior stuff, but even that is fan service done poorly. Here's that line from the show "wink wink".
We do get to find out what happened to Dickie, but that would've meant more if it turned out Tony knew when he sent Christopher after his dad's killer in the show.
Having Tony Soprano as a teenager wandering through the movie here and there but not really being a part of him was a waste.
Prequels are hard, unless you go back far enough where none of the characters are really relevant, you end up winking at the audience and mentioning things that happened instead of focusing on the story.
This movie made me appreciate what Better Call Saul does even more.
Showing us events that we "heard" about, introducing characters we already knew and maybe know where they end up, showing what made a character act a certain way, how they got that scar, it's all fun and good fan service, but you need a story. This movie didn't really have one.