Why are so many directors bad at endings?

Why so many directors are so bad at endings? Season 1 was masterpiece. Season 2 started well but season 3 seemed to have no script at all.

1. Hwang was literally looking for island for almost WHOLE series, just to find it, get there, yell "whyyyyy" and go back... XD This was one of the most ridiculous character script I have ever seen.
2. Why couldnt we finally get answer, why did his brother became leader? Why no answers for anything? I suppose even director Has no idea why, that's why everything was left without explanation.
3. How the hell did this game arrive to USA? Did leader know "Cate"? They looked at each other, smiled. No answers.
4. What was that guard girl at airport even about? Why did that guy lied? Was her daughter even in China? No? Ofc no answers.

Sorry but it should end after season 1. Instead its ANOTHER great series with idiotic ending you wish you could erase from your memory.