Well explained. Depth of field is a critical tool to have ‘on your belt’.

There is a limit to depth of field — something called diffraction (light tends to spread when it goes through a small aperture or across an edge). This causes overall softening in your shot. The smaller your sensor, the larger the opening where this starts to be an issue. This is physics, not lens quality, so you can’t fix it with a better lens.

Anyway, given that you can’t have perfect sharpness from very near to very far, you need to think, compositionally, about where that sharpest-zone should be. I mostly am with Galen Rowell, in landscapes with distant features, I let the distant bits go a bit softer. If anything, it helps with atmospheric perspective. If there’s a single feature I want to draw the viewer’s eye to (e.g. mountaintop fortress sticking out of the clouds) sharpest zone goes there.

BTW/FWIW, if you have an android phone, check out Jon Sach’s DoF app. It lets you change aperture and focal length — and see what happens interactively. It also shows diffraction. Disclaimer: I worked with Jon at one point, but not on PictureWindow.