Fandom is...Funny.
I grew up watching the original show with my dad on WNYW here in NYC. It used to come on after Drive in Movie (which was the program that aired Shaw Brother Kung Fu movies).
I liked the show quite a bit as a kid but I'm also a rational human being with common sense who understood upon seeing the movie in 1996 that the Jim Phelps portrayed in the movie WAS NOT the same Jim Phelps I'd known from the series. And I was fine with that. Much in the same way the Elliot Ness in the movie version of THE UNTOUCHABLES (also directed by Brian DePalma) was not the version made popular by Robert Stack in the TV Series. The reveal of Phelps being still alive after the presumed near TPK at the beginning and Ethan working through what must have happened is my favorite scene in that first film.