Just about give it a 5.
Exactly what was the missile supposed to do? Just allow Sutekh to emerge from the rubble? But it the end he tried to cross through the portal, so why couldn't he do that already? It seems to me that the Osirans didn't really do a very good job of jailing Sutekh, leaving a portal through which he could exert mental influence, and then he can be freed if you just solve a few puzzles. They didn't think it through!
I know the story so well that it's difficult to know how obvious this would be on first viewing, but the missile wasn't aimed at Sutekh's prison. Sutekh was imprisoned in a tomb in Egypt. The pyramid on Mars was transmitting a signal that prevented him from moving, and this was what the missile was supposed to destroy, allowing him to escape. It's never exactly explained how the portal was set up, but I'd assume it was created after Scarman had broken into the tomb, fallen under Sutekh's influence, and brought the Sarcophagus out.
Some of the puzzles do seem a little childish (especially the two guardians, which is a simple logic puzzle I knew as a kid) but others are harder, like the two sets of symbols. In any case, remember that at the time the Osirans imprisoned Sutekh, humans were pretty primitive. Maybe they just didn't anticipate anyone even getting to Mars.