M4 MacBook Pro 16-inch display visibility and color issues

M4 MacBook Pro 16-inch display problems.

I just got a refurbished 16-in M4 MacBook Pro (currently running Sequoia, waiting for the next Tahoe release to update the OS). I'm having vision issues with the laptop's display. First of all, I have to use light mode instead of dark mode for visual accessibility reasons. However, in default settings all of the text is gray on a slightly less gray background, making text hard to read. I've tried increasing the contrast and brightness. This works for me on other devices, but not so much with this laptop.

With other computers, I've been able to customise the color space of the display. I prefer a white point of 6000 with added contrast. This was all adjustable in the past, doesn't seem to be now without a professional calibration device. So what can I do to increase visibility in this new-to-me laptop?