well I doubt just any first year could get through the obstacles. The trio got through because their combination of skills were useful for the tasks. Draco, Crabbe and Gyle couldnt have done it even if they were nice guys. But then again would the professors try toooo hard to protect it, I mean they could have concentrated on stopping powerful spells and completely overlooked the possibilty of simple spells being used. But then again the obstacles were incredibly difficult to get past unless you know how. You wouldnt have a clue how to get past Fluffy without Hagrids advice. A troll isnt the simplest thing to get past.Spotting the right key in a crowd and then catching it. The devils snare killed that guy at st mungos so its very dangerous. The potions needed an incredible amount of logic which hermione says alot of powerful wizards dont have an ounce of. And Dumbledore's is extreemly difficult to figure out. So in fact the chambers are in fact very difficult to get past.