So how do you know the Gospels are cool if other scriptures are not cool?

Two reasons: Why would Jesus come to reform Christianity with teachings of love, and then when he dies instruct Paul to immediately backtrack and replace many of his teachings with more hating scripture?

If Jesus wanted to know something, he would have told us when he came, especially something as important as the nature of Christian morals which Pauline texts change. If Jesus had 35 years to tell us of his teachings and preached about them extensively, why would he just leave some new teachings for Paul to teach when he easily could have just said it while he was there?

I after with everything in Mark, Luke, and John. Mathew is filled with historically inaccuracies over the events of Jesus' life and his teachings. He's has been shown to have a major bias that the other books don't have that clouded his judgment, the others are much more representative of Jesus' actual teachings- especially Luke, who was one of the first historians ever and tried to make his book as accurate as possible.

I know the other gospels are 'cool' because they're the word of Christ, which is what Christianity is supposed to be based off.

IMO it's basically like worshipping Bill Nye and calling him God just because I like his teachings

If Bill Nye was the messiah and came to earth, I would do so.