how to darken print

Canon’s website shows a driver update for your printer available that supports macOS 10.14 Mojave. It was released on 9/4/2019 just weeks ago. You might try downloading an installing the latest software from Canon to see if that deals with your issue.

What color profile does your image file have? Go get the profile open the file with Preview, click on the Info button and check the general pane:

If the profile is Adobe RGB that may be why it's printing dark as inkjet printers are set up for sRGB color profiles, but not the Adobe RGB. If necessary you can change it with the ColorSync Profiler app located in the Applications/Utility folder.

What app are you printing from? Some apps can let you lighten up the image before printing.

Put in new ink.

Then follow what BobTheFisherman suggested.