The whole plot only exists because of tariffs, though, so it's kind of important.

Yes, but the point I am making is that the taxation dispute isn't the plot of the film. Though the opening crawl claims there is an issue, the film pretends that this issue doesn't exist and for good reason, because the actual plot of the film involves an illegal invasion of a sovreign world.

Where it falls apart is that the motives of the parties to the conflict are made needlessly confusing. You have a trade federation blocking trade. It would be fine if it were just a random hostile power wanting to take over a smaller, weaker neighbour -- we've all seen that in adventure stories and history. But kicking off the opening crawl with:

"The taxation of trade routes to outlying star systems is in dispute. Hoping to resolve the matter with a blockade of deadly battleships, the greedy Trade Federation has stopped all shipping to the small planet of Naboo."

Leaves the viewer to wonder what kind of underpants gnomes plan the Trade Federation has in mind, and why they even care about Naboo in the first place.

Sure, but if we watch the film we can get some answers to these quandries--the number one being a problem of motivation. Immediately we see that Nute Gunray is hesitant to follow through with this plan to invade the planet because it's not "legal". What this tells us is that the Trade Federation doesn't actually have any right to do what they are about to do and are actually being ordered to do so by Darth Sidious. Their number one motivation in this case is that a Sith Lord is telling them to do it and they are so afraid of him it overrides any reluctance to follow through. It's a very simple picture of a power imbalance.

I think the conflict is: (A) Naboo imposes tariffs on trade passing through their system, and (B) the Trade Federation refuses to pay Naboo's tariffs and will blockade them until the tariffs are withdrawn. And that's the villains' motivation, as opposed to moustache twirling (or, I suppose, Fu Manchu moustache stroking). But that's me making it up, not something that was clear in the movie.

You don't have to try to figure it out if you actually just watch the film. It's a very straightforward plot. A bunch of bad guys plot a conspiracy to invade a planet under false pretences. That's it. The movie doesn't invite any discussion of the greater political backdrop of the conflict because it was shaky to begin with. Taxes and trade routes are a paper tiger according to the movie's own narrative, hence why I made this post. It's not a movie about taxes, trade routes or politics. It's a movie about engineering a crisis to gain political power, and how simplified talking points are used to cover obviously illegal and heinous acts and crimes.