Two things
There are many problems with the Potterverse but GOF has two major ones. Can anyone explain them?
First, this has been mentioned by others but not to satisfaction, if the whole aim was to bring Harry to Voldemort why didn't Crouch Jr. simply create a port key out of a piece of paper, or any other random object, and ensure, by physical force if nothing else, Potter touched it?
Also GOF shows us plainly that there are alternatives to Hogwarts. In the book Malfoy even says he considered attending another school. So how has Hogwarts managed to maintain its crazy environment (Slytherin house, petty expulsion threats [Dobby's actions], nonsense teachers [Trelawney, Lockhart], physical hazards [doors that won't open, dangerous lifeforms [uncontrolled dementors, whomping willows], the problems only multiply in the later books/films)? It would seem that once parents (either 1/4 or 3/4 of them) learned how their children were being treated the school would either be depopulated and close or else Dumbledore/ the Ministry would have had to totally revise things. In both the books and films the Ministry had been influenced by public opinion so to claim that they had the magical community totally suppressed doesn't click. In fact it's surprising that there weren't numerous benevolent Voldemorts running their own private schools for Hogwarts’s expellees.