That's not niave and that might explain why you gave such a low score to Perfect Dark Zero and actually praised the World Xplorer mode in RR6 which if you had completed you would realise has a number of flaws.
Games like Donkey Konga, Soul Calibur, Zero Gunner 2, whatever, those kind of games you don't need to try everything because they are arcade style and the feel and gameplay is the same and can be judged early on. A certain degree of judgement needs to be used.
Of course a player doesn't have to experience everything in a game like an RPG because the same principle holds. However in a game where each single player level offers something different then yes it is important. Otherwise you end up with the kind of uninformed statements that don't hold up which can be seen in the Critic's PDZ review:
"but I managed to do fine despite blowing my cover again and again."
"Unfortunately, the missions themselves are a mess, and if not for white arrows directing me every which way, I'd never know where the heck I was supposed to go"
"These can also be played cooperatively with a friend, but that's even more confusing"
These statements clearly show very little playtime. I always play with the arrows switched off and the levels have lots of details and areas but don't take more than a couple of tries to memorise all the important routes. And you can only get away with breaking the stealth rule on the easiest settings.
Frankly I think it is ridiculous a person can review the single player portion of a game without actually playing it all the way through. I think I will have to take the future reviews on this site with a grain of salt. You would never find a magazine or a website like Gamespot review an FPS game without playing it all the way through. And that is because they think it is important in order to take their opinions seriously. I just think it is a joke not too. How can a full and proper critique be made when someone has only seen a portion of what the game has to offer. It is no different to watching half the movie and then leaving and writing a review of it.
Oh and SSX if you are talking about PDZ try saying Perfect Dark Zero rather than Perfect Dark, that might avoid the confusion in future.