Well, there are a lot of things wrong with Rogue One: paper-thin characters, a middling pace, a largely forgettable (and, within the mythos, unnecessary) plot.
But the tank – the TX-225w “Occupier” combat assault tank, as Wookiepedia tells me – is the perfect vehicle to address Rogue One’s fundamental problem: a superficial guise and muddled tone.
Because while the film purports to be a gritty war drama – tanks! firefights! no Jedi! – it never fully divorces itself from the character of the rest of the series.
And that has serious repercussions.
Star Wars – despite a misleading title – has never really been about warfare. In the series, wars merely act as backdrop and motivation for the melodramatic blood feuds of space wizards: a former slave is seduced by dark magic and rebels against his mentor (the Prequels); a farmboy learns magic to defeat his fallen father (the Original Trilogy); an orphan scavenger discovers magic and proceeds to beat up some goth kid (The Force Awakens).
The climax of these films usually feature a battle of some kind, yes, but it is the emotionally-charged contest between individuals that form their central focus: Luke vs. Vader (the battle of Yavin), Luke vs. Vader (the occupation of Bespin), Luke vs. Vader vs. Palpatine (the battle of Endor), etc.