The Emerald Dream was created by Freya during the ordering and the first thing she shaped was G’hanir. Amun’thul later ripped out G’hanir from Azeroth, but the roots remained. It would stand to reason that the first Druids were the Haranir who took up residence among the roots and thus have a primordial connection to the Emerald Dream. We simply did not know they were the first Druids simply because the Haranir were secret, as the existence of G’hanir’s roots were a secret for a long time.
Basically, Druidic magic and shapeshifting likely existed long before Malfurion, but Malfurion was the first modern Druid and creator of the Druidic order that we know today.