Why this movie was only good and not great *SPOILERS*

Fantastic acting and casting, especially from the two leads. The problem is, even for the 1990s the plot goes from realistic and great (the beginning train discussion between Huey and Buckner) to incredibly ridiculous. Two drunk small town yuppies decide to kidnap an FBI agent? And then two minutes later a guy running for congress tries to kill an FBI agent (once he knows he's really an FBI agent) and the other cops just follow along without asking any questions? Then the FBI director believes the small town idiot sheriff that Buckner was trying to help Walker escape enough to let him run an investigation while he waits to see what happens? And then the FBI director lets Buckner get away with letting Walker go because of some cock and bull story about Walker getting away from him twenty years ago? Really? At that point it really went from an 8 to a 6 for me, as if the writers were treating the viewer like a four year old child. I guess for once I can agree with the IMDB user ratings because this movie had so much potential with the great soundtrack, discussion of the 60s and 80s, and some great actors giving fine performances, but the weird and way over the top plot just killed it. Even for an 80s or 90s plot this was nuts. I wanted to love it because it was so endearing in a lot of ways, but it just was way too unbelievable. As a sort of weird nostalgia film this is good, but as a film in general this plot is insane at the best of times.