> What worked for printed text has no bearing for what works on an illuminated screen.

Yes it does.

> ... but it is equally important that things aren't too bright. You should avoid using extremes like #000000 and #ffffff ...

No, you shouldn't avoid them. Users are fully capable of adjusting the brightness and contrast of their monitors.

> Believe me, as a 50+ year old, I notice when it's hard to read things.

I believe you. I just don't think your personal experience is relevant.