Yeah, it's kind of hard to come up with a cutoff. There's lots of really old vague theories that had the right idea. Eventually you get to the point where you're thinking that there was probably a caveman somewhere who built a fire in a cave and wondered what would happen if the whole world filled with smoke.
From a science perspective, Svante seems to have mostly had it, but applying the science really started to coalesce in the 1950s. The American Petroleum Institute actually funded a study in 1959 to figure out if they were really going to destroy the planet. Their findings were a bit more extreme than what actually worked out, they thought New York would be underwater around 1990, but it pretty well established things.
Source: https://www.timeextension.com/news/2025/02/14-percent-of-north-americans-still-play-gaming-systems-released-before-2000
References this site: https://www.consumerreports.org/electronics/media-formats/holding-on-to-physical-media-a3747629925/
Actual data here: https://article.images.consumerreports.org/image/upload/v1718112414/prod/content/dam/surveys/Consumer_Reports_AES_May_2024.pdf
Actual question references "Classic videogame systems that came out before 2000, like the NES or GameBoy" and "used at home in the past year" of which 14% responded yes out of a group of 2022 surveyed in North America (demographic details available in link).