You probably have VERY slow hosting, did not compress images, and are using a bulky template if I had to guess. Who's your hosting?
As other people said, it's likely your hosting, or you use a bulky responsive template as shown by "Prioritize Visible Content" and "Compress Images". I don't believe Google uses PageSpeed to determine ranking, as a lot of the criteria come in conflict with some of the things Google provides themselves, such as Google Fonts.