It seems (based on what has come to light so far) that Trump Jr found that what was offered wasn't helpful and it wasn't used. So, he didn't actually break the law against foreign collusion in elections. But it is also clear that he was willing to do so. And it's also undeniable that Russia *was* trying to influence the election. So, whilst this particular incident may not be significant in itself, it does underline the need for the Comey/Mueller FBI investigation, and the wrongness of Comey's sacking.
But unless there's evidence that Trump remove Comey because of where the investigations were going there's no way to prove obstruction of justice...
And if they found his "tapes" ... that would be 100% fake news, blame Obama, sack someone else, drop another bomb somewhere to distract everyone, and everything will be OK.