Harry should have figured it out

In The Goblet of Fire movie Harry dreams about Barty Crouch Jr and Voldemort in the opening scene and knows Voldemort sent Crouch after him. At the Quidditch World Cup he may or may not have seen his face when Crouch sets off the Dark Mark. That should tell him that this guy Voldemort sent after him does indeed exist.

Then before the second task Myrtle mentions that someone has been disposing polyjuice potion down the drains. Then the very next scene after seeing Crouch Jr in Dumbledore’s memory in the pensieve, Snape says he knows Harry and his friends are brewing Polyjuice potion and he was going to find out why.

At the very least this should’ve set off alarm bells that it was possible Crouch Jr was at Hogwarts using polyjuice potion to imitate someone, given that Harry knows exactly how it’s used. ….and that that someone would have to drink it regularly to keep up appearances. Who else was known to take swigs of an unknown drink at all times other than MadEye Moody?

Just rewatching the movie now and I’m having these thoughts. Been a while since I read the books so I don’t remember if all these clues were given there as well.

Dumbledore even says he keeps getting close to the truth and then it all slips away but that was possibly because he didn’t have all the information (about the polyjuice potion and whatnot), whereas after his conversation with Snape I feel Harry would have and should have been able to connect the dots. I’m sure Dumbledore would have been able to if he had known all this.