All replacement body parts junk?

[Ace in the hole]

I am fairly new here and have been researching many things on these forums. Man there is a lot of great info here!

One thing that strikes me as odd is that the general consensus seems to be that there are a lot of different replacement parts out there that are junk, take tailgates for example. Why do some of the venders that support this forum and are so highly reguarded continue to sell them if they just plain don't fit right?

I have been thinking of what I need for my truck and how I want to go about repairing it. Sure would be nice to know if I want to sink money into replacement parts that if you buy from xx vendor or xxx vendor you know you will be getting stuff that will fit right the first time or at least have minimal headaches trying to make it fit.