In the February 2019 Update its effect was changed to include wonders from Ancient, Classical, Medieval, and Renaissance eras, instead of just Medieval and Renaissance.
Gothic Architecture replaces the earlier Corvée as the Economic Policy boosting Wonder construction for the Medieval and Renaissance Era. It is arguably much more useful simply because you have more Economic slots in later governments...and consequently, more opportunities to use it. But even more importantly, Wonders from these eras are some of the most powerful in the game, and include three of the four wonders which add extra slots in any government (Alhambra for a Military slot, Forbidden City for a Wildcard slot, Potala Palace for a Diplomatic one). So, you are well advised to use this Policy and try to build wonders at this point in the game.
Civilopedia entry Edit
Distinguished by ribbed vaults, flying buttresses, pointed arches, overlaid tracery … and gargoyles, lots of gargoyles. Gothic architecture dominated construction of monumental European buildings from the mid-12th through the 16th centuries. Arising from Romanesque styles, it was the architecture of choice for cathedrals, abbeys, castles, palaces, guild halls, and all sorts of buildings meant to impress and awe the commoners. With cavernous interiors and soaring rooftops, these were perfect for the pomp and pageantry kings and bishops so loved. Sadly, a slew of Gothic revivals spanned the mid-18th through early 20th centuries, largely for stunningly ugly university structures, replete even with gargoyles.