Buy a brother printer instead. They may be a bit more expensive, but their easy mantainance and the amount of bootleg ink you can find online makes it worth the extra price.
Last time this came up, people were quick to bring up brother, and others (and that was new) to mention that brother started to do the same crap (limiting 3rd party toners). So I really don't know what to think of them anymore.
I could be in the market for a b&w laser printer/scanner soon so I'll keep an eye on replies here.
Change the print settings to a higher dpi and/or adjust the density. You might have to fiddle around with some other settings in there to get it how you like it. Generally if the test page prints okay there's something wokny with the print settings for whatever app/driver. Test pages print with preset settings, so they are standardized.
Could be unrelated, and you might just have issues with the printer head, but I've closed a more than a few tickets back in the day for people by adjusting print settings for them (these were brother label printers so YMMV).
Here's a generic KB for doing this on most models of Brother printers: