Pub player expectations.

Just a quick view on things, i'd consider myself a casual player. I go to college and am rarely on, but I enjoy the occasional LoL game. I'll admit that some of my builds/actions in-game are anything but inspirational sometimes, but what is it with all of these great, over-the-top players expecting to get the best support/teammates when it comes to pub games? Each will yell at me for building a certain item, and each will tell me to do something differently...when I do what the person before tells me, the next tells me otherwise and decides to rip me a new one (I take any in-game suggestions as constructive criticism). What's everyone's take on this?