The Atlantic article you linked to included many quotes by law professors saying information is clearly a “thing of value” and Don Jr. broke the law, in addition to the quote you posted from a law professor saying he didn’t.
That being said, I’ll concede that the illegality of his actions are debatable, and it would have been more accurate to write the sentence this way:
“But we do know this: senior members of the Trump campaign — and now Trump administration—tried to collude with Russia, perhaps illegally.”
My main point, however, is about three people at the top of the campaign pursuing an opportunity to work with the Russian government. Presidential campaigns are time consuming, and it’s hard to get a meeting with both a top adviser (Kushner) and the campaign chair (Manafort). They wouldn’t have taken the meeting if they weren’t serious about it.
The emails provide hard evidence they knew the meeting was with a Russian government representative and part of Russia’s efforts to assist their candidate. That contradicts their long-running insistence no one from the campaign worked with Russia in any way.
On the legal question, it’ll be interesting to see if Junior, Kushner, and/or Manafort get charged with anything relating to campaign finance, making false statements — which especially applies to Kushner on security clearance forms — or, depending on what they did after, obstruction.
Finally, if you think this whole issue is unimportant, we’ll have to agree to disagree. I think the issues you mentioned are important, but I think collusion (possibly criminal) between a presidential campaign/administration and a foreign power is important too.