There seems to be an increasing trend for PDFs and websites to use grey text instead of black. Even Google Sites is doing this (sorry I can't override this!).
For web pages, there are some Chrome / Edge extensions available. The best that I can find is "Darken Text". This requires you to press the DT button to activate it for a web page, which is a little annoying because you have to click it for every web page.
However it works pretty well.