Krita lacks a lot of tools to work with photography. It's OK with general image manipulation but you have to really struggle to do anything that's not digital painting.
That said. The left side of GIMP is wide because the tool options are under the tool's icons. While Krita has them on the top as a bar.
Both programs let you move and change the layout to whatever you want, though. No one serious about using either program uses the default. There's a bunch of stuff you don't need to use that only takes up space when you're just doing one particular task. Hence why saving and reloading layouts is such a powerful feature.
EDIT: Here is, for example, my layout.
Also, the little logo on the corner has a purpose. It's a small area where you can drag and drop any image file from your file explorer and it will automatically open the file for editing, instead of pasting it on the current open project as a new layer. It's super useful.
You can press the TAB button to temporarily hide all menus. It helps when working on small screens.