I first saw SNF about 15 years ago & also felt a bit underwhelmed by it. But it was likely because the movie was dated & i regretted not having watched it at around the time it came out. I likely would have found it sensational had i seen it then. I absolutely loved the soundtrack & the dancing sequences which i still watch on YouTube occasionally. When i was growing up i just missed the disco era & i have always said that if i could go back in time i’d like to experience the height of the disco era.I was underwhelmed with "Saturday Night Fever", when I saw it a few years ago. But "Taxi Driver" is a true Scorsese classic. It gets better with each viewing.
As for Taxi Driver i saw it once but was somewhat underwhelmed mostly because i was likely too young when i saw it. That’s one movie that i plan to re-watch soon!