I Saw A Bear on YouTube recently did a playthrough of the original game and the timing was pretty brutal and some of the situations where you had to jump and turn at the same time and get a very specific hitbox to catch a ledge correctly.
Are there any games akin to the first Splinter Cell? Where there's no run n gun option? I played one of the more recently released ones and at the end it's just basically a giant firefight and it kinda loses the thread of the original.
Double Agent was actually great, but the only way to play the true one (IMO) is on Xbox, PlayStation 2, GameCube, or Wii. This version was made by Ubisoft Montreal who developed the first game and Chaos Theory. It is at the same quality level as those two.
The version of Double Agent for the 360, PS3, and PC was developed by Ubisoft Shanghai who also did Pandora Tomorrow. Like you said it is okay, but it is pretty blatantly different from the other ones. Different engine, different vibes in general, and honestly just inferior in most ways.
If you're into tactical third person shooters, I can only recommend SOCOM especially the second part!
Tactical Squad Based Shooters, where rushing in is seldom the answer.