WORDPRESS: Is there a benefit in having a website designed by a designer vs running with a WP themed site?

Honestly, I think custom designs are a thing of the past especially with theme builders like Divi. They are so customisable that it defeats the purpose of paying for a custom theme.
That’s not to say that a developer can’t do a lot to improve the look of your site. Build the basics yourself using the WordPress course, then get your dev to snazzify!