Women have been wanting comparable rights to men since before written history, yet most people would say the women's suffrage movement started in the mid 1800s. The original user wasn't saying trans people didn't exist until recently, they were likely saying there wasn't previously any serious effort at accepting them in (American? Western?) society, or at least no where near the magnitude as today. Basic public tolerance may not be good, but it is much better than even just a decade or two before.

Paris is Burning isn't a film I had heard about before, probably because it's older than me and I haven't been paying attention to queer spaces long. And if that user is 45 now, they would be about 10 when it released. Pretty reasonable to not have it on their radar considering it is R rated. Still, they shouldn't assume trans communities didn't exist just because they were not aware of any back then. That's just a mistake.