Quality of life apps fix small daily annoyances: screen color temperature, external display brightness, cursor visibility, grayscale mode and keystroke display. Individually they are minor, but they are the kind of utilities people install first on every new Mac.
f.lux warms display colors in the evening and offers more control than Apple's Night Shift, while Shifty adds menu bar controls for Night Shift itself. Lunar adjusts brightness, contrast and volume of external displays, and KeyCastr shows your keystrokes for screencasts and presentations. Most are free and small, so check support for your macOS version and display setup.