It's not just blind people, but also people with reduced eyesight. As I'm getting older, I really appreciate good contrast and the possibility to zoom in without breaking the layout.
People always forget they're one unlucky event from losing their sight, hearing, dexterity, or more. Hell, like you say, even aging's enough to do it. Accessibility suddenly becomes a lot more important when you're on the other side of the "not a priority" talk.
If Tailwind lends itself to using pixels instead of relative units for things that should be relative (like font-size, line-height, etc.), that's a problem.
For those users, the HTML elements matter less unless they're savvy users who have custom user stylesheets to selectively adjust the appearance of content instead of changing everything on the page by zooming (e.g. make links, buttons, paragraphs, list items bigger and/or a different font or weight).
This is not true. Tailwind defaults to rem as the underlying length unit for almost everything. You have to go to extra effort in most cases to use px.