Saw your post on this. Love seeing someone other than myself play it! I agree that some of the mechanics did not age well, and the Destroyed Subway level was hard to navigate at first (I literally struggled on the C4 part, had to look up walkthrough back then to see what to do), and some of the stealth missions were haaaaard. I couldn't even finish it in Hard Mode, kept getting slaughtered in the Catacombs level.
Not saying GO PLAY THIS, but if you want, try out Syphon Filter 2. The mechanics there are so much better and the objectives are easier to navigate, plus the story is captivating and best out of all the series.