This makes it an extremely uninformed article. The mainstream witchcraft (i.e. wiccan) movements stem from Gerald Gardner's attempt to reconstruct Italian and British witchcraft traditions and turn it into something acceptable for modern audiences. Both his specific reconstructions and the problems with them have been well documented (see his own books and those of Valiente).
In many way what happened with modern witchcraft is similar to what happened with modern Yoga traditions (see Mark Singleton's book the Making of Modern Yoga), in that a few people tried to create mass marketable phenomenon by taking some old traditions and then creating a consumable package. Obviously this often comes with overstated claims considering the guru, authenticity, etc. Then it also creates identity movements where people create an identity around their new belief system.
As far as what various pagans did in the Roman empire and how many of those traditions were gradually eradicated by Christianity, some of those things are well documented and some are not, partially because of the presence of many non-recorded mystery traditions in ancient Rome.
As far as people choosing a "pagan" identity as a reactionary counter culture vis-a-vis a perceived mainstream Christianity that also clearly exists where Christianity is mainstream. In various forms it seems to have merged with other reactionary version of feminism.