I just downloaded and started using the program, and for the most part I like it... except that the canvas draws WAY darker than the color that is selected. If I paste a photo into the canvas, darks lose their detail into black. Even worse, the color that I select using the color picker is not what it draws on the canvas, it draws something much darker. This basically makes painting impossibly tedious, and will ruin anything I do manage to get out of it. Is there a fix for this?

This is a bug related to the default settings. Just go into preferences and check if 'black point compesation' is on. (So, setting->configure Krita->color management, check if blackpoint compensation is on.)

Even just looking at that page might fix it.
Otherwise, make an 8bit image instead of 16bit or higher. 8bit is per channel, so that's 32bit as you are usually familiar with it.

I have exactly the same problem with too dark canvas. But changing preferences doesn't work with saved files, only with new.