Maybe I'm an idiot and completely missing something here, but couldn't this essentially be accomplished by enabling screen reader software on your own computer and turning off your monitor?
By the time someone reaches 50 there's a good chance a proportion of text on their phone, web, computer and even groceries that is becoming unreadable without glasses.
Most app developers haven't a clue. Most of us 50 somethings hadn't a clue 10 years ago! Ctrl + in a browser is a brute force solution. Android's is even worse and a lot of what you want zoomed simply isn't, but it enlarges the parts you can read just fine.
Compared to many of my age I'm lucky and rarely need glasses, but already it's very annoying!
Something like this could be as helpful as when I first saw colour blind simulators 20 years or more ago.