There are other vision conditions where people cannot see letters in dark mode that well. Apps and websites should just follow whatever the OS setting is, no matter the motivation of the user. Even if it’s just a matter of taste and not some form of eye sight condition, it’s just as valid.
I have a beefier version by that same brand. It’s somehow on sale almost all the time on Amazon. It works fine, the glossy finish of that screen is super dumb because you basically have to consciously put the cable on the back side of the power bank or it’ll scratch the screen like crazy.