Can we please dispense with the notion that what Trump Jr. was doing was anything remotely related to opposition research?

Why? Because you think that would be inconvenient to your argument? That's clearly the very definition of what he was doing, regardless of whether or not he was ever a working for a firm that specializes in doing that. Amateur opposition research is still opposition research.

Whatever information the Russians offered, they acquired it illegally, and clearly the Russian government and Russian intelligence services are not an opposition research company.

We don't know that any information was offered, and there's no evidence in any of the emails that suggested that the information that was supposedly on offer was acquired illegally. It was before the DNC hack was even publicized.

They are state actors that intended to interfere with the regular operation of our government and election. They disrupted the peaceful transfer of power and what they wanted in return was not simply pay for a job well done.

The law that Trump Jr. is accused of breaking makes it a crime to solicit donations or contributions from any foreign national. Whether or not someone is a "state actor" has no legal significance. Maybe it should, but it doesn't.

The payment they asked for was clearly and obviously policy concessions related to the Magnitsky act, which they apparently got in part at least in having their case dropped and Preet fired.

Could you point to the tangible evidence that makes that clear and obvious? Or do we take wild, baseless speculation from certain members of Congress who can best be described as "pieces of work" as fact now?