I'm 53 and I'm at least five years behind getting my specs sorted out - they are currently perched right on the end of my nose now and I have to get the angle right sometimes (astigmatism).
That page is nearly fine for me but I just hit CRTL + to scale up. That works for me.
That page is pure text with no or at least minimal fiddling. You have your solution for your use case and I have mine. A blind reader will also have their solution, so they can even access it. Thanks to the simplicity of the source: all solutions to accessibility are also going to be reasonably simple.
I think that Dan understands how to communicate effectively - keep it simple and don't assume that eyes will read your words. You can trivially (and you do) fiddle with the presentation yourself for your own purposes.
I think that if you don't like the presentation of something like this then you could reformat it yourself, prior to engagement. Dan has kindly provided his message as a simple text stream that can be trivially fiddled with.