Director Richard Linklater has made conventional movies before, but none quite so anonymous as “Last Flag Flying,” a follow-up of sorts to Hal Ashby’s much-lauded 1973 “The Last Detail.” Like that film, it’s based upon a novel by Darryl Ponicsan (who co-wrote the screenplay with Linklater). The book was a direct sequel to “Detail,” featuring the same three characters more than three decades later. The script changes their names, perhaps in an effort to avoid direct comparisons, which are bound to be invidious. But the alteration fails to disguise how inferior this well-meaning but pedestrian picture is to its now-unacknowledged predecessor.

That’s rather surprising since in many respects Linklater would seem a perfect choice to take up Ashby’s mantle. Like the older director, he favors a direct, unostentatious, naturalistic style that can come off as ragged but works when the material is honest. (The homely look of the picture—shot by Shane F. Kelly, with a production design by Bruce Curtis, follows that tendency as well.) Too often here, though, things ring dramatically false, and what is meant to be deeply moving is bathetic instead.

The set-up is a simple one. In 2003 meek Larry Shepherd (Steve Carell)—the successor to Meadows, the character Randy Quaid played in “Detail,” the young guy being transported to the naval prison in Portsmouth—finds his way to the run-down Norfolk, Virginia bar owned by Sal Nealon (Bryan Cranston), a cynical, sarcastic type who’s the descendent of Jack Nicholson’s Billy Buddusky. Though they haven’t seen one another in decades, Larry, or “Doc” as Sal calls him, asks Sal, who served with him in Vietnam, to accompany him to Dover Air Force Base where he’s to claim the body of his son Larry Jr., a Marine killed in Iraq and scheduled to be buried at Arlington Cemetery.

Not only does Sal agree, but together they travel to a nearby Baptist church to recruit the third member of their old crew, Richard Mueller (Laurence Fishburne)—erstwhile Mulhall—in the mission. Mueller, who was known during his time in the service as “Mauler,” is now a pastor, and reluctant to go along until his wife Ruth (Deanna Reed-Foster) insists: the fact that Larry also recently lost his wife to cancer only adds to his pathetic quality.

So the trio set off for Dover, where they meet Larry Jr.’s best friend Washington (J. Quinton Johnson) and learn the true circumstances of the boy’s death—which are a bit different from the tale of valiant combat offered by attending officer Col. Willits (Yul Vazquez). The news disturbs Doc, and he decides, against Willits’ advice, to transport his son’s coffin back to Portsmouth for a civilian burial. And of course he’ll be accompanied by Sal, Richard and Washington.

So in essence this is a road movie, and an extremely talky one at that. (Actually, it could have been substantially shortened if Sal weren’t constantly introducing a new colloquy with one of the other characters by saying, “Can I ask you a question?” and then doing so. It’s a crutch so frequently resorted to in order to raise a new subject or recollection that you grow very tired of it; too bad editor Sandra Adair was unable to finesse the transitions better.)

That’s especially the case because Cranston offers what is essentially a one-note performance as Nealon. There’s very little shading to his turn, which comes off as particularly weak when compared to Nicholson in “Detail.” Carell, following his extrovert imitation of tennis provocateur Bobby Riggs in “Battle of the Sexes,” goes the opposite route here, playing Shepherd as such a shy, recessive guy that he practically disappears. Fishburne exudes his usual stabilizing force, but his character is a pretty pallid one.

And what, ultimately, is “Last Flag Flying” about? It’s about these three old comrades-in-arms finally coming to terms with an episode from their past—involving a recreational use of drugs that made it impossible for them to alleviate the pain of a wounded friend—about which they’ve all felt guilt over the years. That leads to one of the various impromptu detours they undertake during their trip—a visit to the frail mother of their long-dead buddy, played affectingly by Cicely Tyson. There’s an ironic conclusion to the visit in that the story they tell her isn’t unlike what Col. Willits had told Shepherd about the death of his son—both are basically well-intended fabrications. But the screenplay doesn’t do much with the comparison.

That’s surprising, though, since otherwise the script goes pretty consistently for the obvious. The result, despite the starriness of the cast and the presence of Linklater, is an undoubtedly sincere but mediocre paean to military comradeship.