Hiding things is a good way to make the design visually as minimal as possible. What is not immediately needed can be put away. Users can reach for them when needed.
This is a good approach for things that are actually only needed in some cases. Like for example the editing controls. As long as there is no text selected the editor menu actions wouldn't do anything anyway. You also only need minimal action once the menu is visible as it's close to the position of the previous action. There's also no need for additional clicks to bring the menu up.
Another thing that is usually hidden, especially on small displays is the main menu. There is just the burger menu on the corner revealing all the menu items once clicked. But revealing the menu and selecting your destination requires twice as many clicks as a menu that displays the options right away. Of course showing all the menu options is often not possible due to the sheer amount of menu items. But I strongly believe the main actions should be visible all the time as long as the context doesn't say otherwise (for example the editor view hides everything not required for writing).
Keeping sll menu items visible also enforces focus on actually minimizing the amount of those menu items. Instead of creating new menu items without limits you need to carefully consider the necessity of every single item. This way it's not just the visual design that stays simple, but the site structure will also remain clean and simple.