I had a problem with a Brother HL-L6200DW with poor print quality on Widows 10. I resolved it as follows:

In the “Type here to search” box – type in “Printer & Scanners”

Select your printer – then click on the “Manage” button

In the new window select “Printing Preferences”

Select the “Advanced” tab

Select “Other Print Options”

Select “Improve Print Output”

Select “Improve Toner Fixing” then “ok”  – then “Ok”- then close the settings window