"The officer then opened the backseat door where I was sitting and asked if I was paying for the ride."
Just don't answer. You don't have to. Even if you knew the law had passed in Denver, why would you answer? It cannot help you.
The police are people, subject to the same quirks that everyone else is. Just as with any organization, the culture also has a part to play (hopefully you aren't in an area with heavy police corruption.)
If you are riding as a passenger and you don't otherwise have anything to worry about, then there is probably more risk to going against the police than by simply cooperating even if you don't have to. If you have something to hide and you are the driver, then you want to be pulling every trick you can.
Unless being an Uber driver is a criminal offense, then I assume they could only write you a ticket that you could then take to the courts. If the police aren't up to date with recent changes to the laws, the the courts should be.
Just be a nice person, even if you are encountering someone in a position of authority who is having a bad day.
Simply inform the officer you cannot answer any questions. You can be a nice person and still exercise your rights.
The right way to handle a police stop (in the US): https://www.youtube.com/watch?v=eDJrQBwJpqk
Starts at 1:10
"Sorry, officer, I don't understand your question."
"Are you paying to be a passenger in this vehicle?"
"I'm sorry, officer, I want to help you, but I just don't understand how this involves me. I'm just a passenger here."
Most cops will just give up asking the question there. If the officer pushes the issue, he's being an asshole, but you can still very politely invoke your fifth amendment rights: "Sorry, officer, I should have an attorney present to help me with these questions."
At that point, answers to any further questions (if any: standard police policy everywhere is to cease questioning immediately) are completely inadmissable (Edwards v. Arizona, 1981).
You can beat the rap, but you can't beat the ride: that's true. With that said, the cops who will bring you downtown for asserting your rights are exactly the cops that you really shouldn't be talking to.
(IANAL, FWIW; I'm just an occasionally rude anti-authoritarian citizen who has to mentally practice polite assertion of my rights so I don't accidentally piss off cops who, in their view, are just doing their jobs.)
You're not dodging the question, but offering a well-understood reason, and the reason involves something real but external to both yourself and the LEO.
They are asking questions in a leading way, its how they are trained. You just have to be diplomatic and nice about it.
I have been stopped before and asked how fast I was driving. I simply said I was not sure but I thought it was at the speed limit. Unless the police have evidence they can only have a talk with you.