When printing a scanned object, paper is all gray

Unfortunately that is typical. You can set the copies to be darker, but often that just introduces gray areas that should be white.

Better to just scan and then print the pdf.

I have an old Kindle e-reader that I can barely read anymore. The text is not black anymore but light gray. There is no fix for it as it's simply a worn-out display. The earlier virtual paper displays had a finite lifetime of about 2500 hours I learned from doing research.

I bought a Kindle Paperwhite to replace it. I guess it will also wear out but hopefully technology has extended the time before it fades into oblivion.

You are probably out of ink in one or more cartridges. You need to do a diagnostic print and take the print to the ink supply vendor to get the correct replacements.

If your background is "Black" it's going to print it all black, change your background color to "Gray" and your machine will then print a gray background instead of black. Also note that when you print a black background your toner life expectancy will be no where your expected yield ratio is. Average yield is 5% for X (X meaning size of cartridge) amount of printed pages. If your printing a black background your utilizing 100% yield coverage. Not sure if this is the answer your looking for. However basic black and white printing with a black background will print the page completely black.

You have two options for scanning text. You may explore both of them and see which is better for you. Either way, you will have to make friends with manually changing the scanning settings, because simple presets often are not suited for every case.

First is to use Grayscale mode, and a minimum resolution of 200dpi. This should give you satisfactory text quality. If you want to print the text afterwards, 300dpi would be even better. You may want to increase contrast, to get the letters more defined and eliminate most of the background toning.

Second is to use Black and White (monochrome) mode, but in this case you need to set the resolution higher, preferrably to 600dpi. Also in this case you will have to play with the Black/White threshold in order to eliminate background "dirt" appearing as black artefacts.

If you scan the documents in order to process them with OCR software, usually the OCR application will give you suggestions on how to set the scanning parameters to obtain good results.

you need to select the right tape for your machine. You can't change how it prints except by changing the tape. Brother has many colors to choose from.

It's never going to be perfect (unless the background is quite light in colour), because the copier basically "sees" the coloured background as "gray", and the darker the background the more "gray" it looks. Try setting the original type to "photo" mode, and then adjusting the exposure a little lighter/darker....that's all you can basically do.

When was the drum replace? Recently? Could it be time again?
Was it a remanufactured unit?
Regardless of all that, It sounds to me like the drum is failing.

change the drum unit
if the problem dos not solved clean the scan unit

Does your scanner software give the option to choose different modes...grayscale, color, black & white?? This sounds like it's scanning in grayscale....if you can change it to black & white, the background should remain white.