Sorry, but I totally disagree.
There clearly were multiple crimes.
Joe demanding Shokin be fired was completely illegal, but making US foreign aid dependent upon the firing is not just extortion, but criminal abuse of congressional allocations.
The illegal kickbacks to Hunter, through Burisma Holdings, are just the cherry on top.
And no, Attorney Generals do not call heads of state, and an Attorney General can't call a lower level because they won't know who to call.
Especially since the whole point is that what one has to investigate is the firing of Shokin, which is the equivalent of the Ukraine Attorney General.
So YES, it not only was perfectly legal, but it was the ONLY way the situation could be handled.
In fact, the investigation is STILL needed.
It is criminal that we still have NOT gotten the results of this necessary investigation.