Google thinks my webpage looks bad

What is the name of that theme, and where did you get it from?

Does it look ok if you temporarily switch to the Twenty Fifteen theme to check?

With WordPress this is very typical as your robots.txt will prevent Google’s fetch feature from grabbing files within wp-includes & wp-admin. These files are critical for Google’s bot to get a view of the website like a normal human were. We actually wrote a blog post about this today since so many people were notified by Google about their bot being unable to access specific CSS & JS. You may find it helpful, it also provides a guide to resolve the issue: https://www.wpcover.com/2015/07/28/googlebot-cannot-access-css-and-js-what-you-should-do/