You can’t change default system font of Windows 10 from settings app or control panel so that you can change the fonts of icons, context menu, properties or dialog box. If you are deadly eager to change the fonts then you have to tweak your registry editor. Here is the steps to take you through to see how to change default system font in Windows 10

1. Open registry, look for HKEY_CURRENT_USER\Control_Panel\Desktop\WindowsMetrics.
2. On the right you have various keys like "Caption font" & "Icon font" etc...
3. Select the font you want to change and rightclick, then choose "Modify".
4. A little windows will open with the name of the registry key and on the right the font name.
5. Replace this font name with the font name you want (watch spaces).
6. Done. Log off or restart your computer to take effect.