The new version of Acrobat moves tools to the left and navigation tools to the right without giving an option for users to customize the location. Having page navigation on the right is unergonomic because the natural reading order is left to right, and people click bookmark titles and page numbers before reading the page content. In books, the table of contents comes before the main content of the book, and you flip rightwards after choosing a chapter to read.

With navigation on the left, the tools would be on the right-hand side in the new version. This makes intuitive sense as most people will pick up actual tools (like hammers, screwdrivers) with their right hand.

All other Adobe software gives users several UI options. For example, Adobe Photoshop has several layout configurations for users (Essentials, Graphic and Web, Photography, Painting, etc.). There is no reason Acrobat cannot give users similar flexibility, especially when it comes to a configuration (i.e. bookmarks, pages on the left) that has been consistent for over a decade across all major PDF readers.