5/10
Unfortunately, even by the standards of its own time, the mission structure was fairly weak, and it has only aged worse since then. The repetitive gameplay eventually dragged the whole experience down.
Since the story is such an important part of this series, that repetition inevitably affected how I felt about it as well. While I liked the presentation and the core premise, I found the narrative itself a bit underwhelming. Without the story fully carrying the experience either, the game ended up becoming a little tedious for me.
I also want to give a quick mention to the DLCs. Since each one tells its own self-contained story, they ended up being the highlights of the game for me from a mission design perspective.