A page builder gives you a visitor-side view of your website, and allows you to place content visually on your website. This is the same principle that is often used in hosted “website builder” solutions like Wix or SquareSpace. Do you need one?
Opinions vary about the suitability of the Gutenberg editor as a replacement for WordPress’ current WYSIWYG editor, and many question Gutenberg’s ability to challenge “drag and drop” website builders like Squarespace, Wix, or Weebly. Other WordPress page builder plugins, like Beaver Builder, seem to meet this competition more head-on.