I have an astigmatism as well, but I only started wearing glasses for it in the mid 90s (I was born in 1970). I was told at some point that I'd be wearing glasses for the rest of my life because there was no way I could ever do contacts (not that I'd ever want to go sticking something in my eyes on purpose).
I've got no issues with dark mode - in fact it was a relief when I could finally get it, either by hook (stock iOS/MacOs) or by crook (jailbreaking my iPhone/theming my Macs).
That's pretty common I believe. Very little websites or backgrounds are true black so often dark mode is a darker grey than anything and if you use things like True Tone it can make the white letters blurry when mixed. Find a website that uses a true black (e.g. 9to5mac) and with True Tone off text are still visible. However, dark text or light backgrounds will always be more legible.