Hi Tom!
That Robots.txt config is pretty redundant.
To acheive what you what, thy this:
User-agent: *
Disallow: /wp-admin/
Disallow: /wp-includes/
Disallow: /wp-content/
Allow: *.js
Allow: *.css
Just 3 things to note here:
1- That User-agent:* and those disallows blocks for every bot to crawl whats in those folders.
2- When blocking /wp-content/ you are also blocking the /themes/ folder and inside are the .js and .css files. Blocking those files cause to googlebot not being able to render correctly that page and see it different from what a normal user would see.
3- Those Allow:/ dont prevent the disallow.
To try that configuration, you can use the robots.txt tester in search console, just inder the Crawl menu.
Remember that by default google considers that you are not blocking nothing.
More info here: The web robots.tat page
Hope it helps.
Best luck.
GR