I had no idea what I was in for, and as a 15 year old, I felt twists and surprises, and organic game reactions to things I did that blow my mind even today, and imo still haven't been matched. And leveling and skills truly mattered and were tied into the game. Inventory management and ammo was interesting, the interface was perfect. It also had a kind of intellectual curiosity (characters talking competently about surveillance state and capitalism!) in the dialog that I only ever felt in, say, Alpha Centauri and later, Disco Elysium. It's still the best PC game ever imo.

Edit: I think the most important thing about its legacy now, is that it engaged with conspiracies in a fundamentally different way, more like 90s X-Files style fascination and curiosity than anti-intellectualism of Alex Jones-style rabid misinformation. A critical nuance that gets lost when conspiracy cranks try to claim Deus Ex as theirs.

Edit 2: Respectfully, contra the article, if anything I think there's not enough hagiography surrounding Deus Ex. It's either beloved or not known, and the latter is the crime that needs rebalancing as it represents an example of what's possible in passion project game design that I think is just as important as it ever was. That matters infinitely more to me than sidecar questions of how more or less "living" it's game world was relative to its predecessor System Shock. I also think the analysis is a little bit off to criticize DX's three-choice ending as being too on-rails relative to System Shock, which is a one-stop boss battle that lasts like 15 seconds.