You can change both if you like (it's one of the first things I do whenever I install GIMP on new systems)! In 2.10, you can change the icons in Preferences under the Icon Theme section, and remove tool groups in the Toolbox section.

In 3.0 it's even easier, as both options are available in the Personalize tab of the Welcome Dialogue. I'm hoping this will help make that feature more discoverable. :)