There are a couple major differences between the NK and Russian situations.
Russia just attempted assasination in the country of our greatest ally. Our duty is to stand with our ally’s who have just expressed the wish to punish not praise Russia.
NK on the other hand is threatening two very tight ally’s Japan and South Korea who both supported increased peace talks and American help in the situation.
So in one case we are working against our ally’s and in the other we are working with them.
The second major difference is that we did not invite Kim Jong Un to the Whitehorse, we are entering talks but not in the symbol of American freedom.
A third difference is that NK is a bad actor with their nuclear program but has not actually attacked America. Putin and Russia just attacked the 16 election and the heart of American democracy.
These issues don’t have to do with collusion, you are conflating two issues. Regardless of the Trump team, Russia did interfere with our election. To invite him to the Whitehouse is to basically say that wasn’t important.
I doubt the NK talks will be productive but I am not morally opposed to them. Inviting Putin to the Whitehouse on the other hand is despicable.