If the Infernal Hammer was considered one of the best forging artifacts one could get their hands on if one wished to create a lot of Fire-attribute items and equipment, then the Hammer of Primeval Origins thought of emulating was one step above it, having the ability to forge Fire-attribute equipment that exceeded the Infernal Hammer in terms of quality.
However, the Hammer of Primeval Origins was not only limited to equipment of the Fire-attribute. As Valyr had chosen to emulate a forging artifact that either had no attribute or had multiple attributes, the Hammer of Primeval Origins was an artifact that fit the criteria, more specifically the latter.
Items that had been forged with the help of the Hammer of Primeval Origins, whether it be Fire-attribute, Wind-attribute, Water-attribute, or Earth-attribute, had stats that were significantly greater than even forging hammers attuned to one of the specific attributes itself.