Contrast ratio between the link and the surrounding text is at least 3:1 sounds easy to achieve, but in practice it rules out almost every color, so it's a nonstarter in almost every case; WebAIM actually has a good article showing how few colors actually can hit a 3:1 ratio: https://webaim.org/blog/wcag-2-0-and-link-colors/.
Sure, you could make links bold, but no one does that for a reason: it looks ridiculous.
The thing that I find particularly egregious about that rule about it is how this doesn't even seem like it helps that many people. A screen reader user would necessarily know that an element was a link regardless of color, and even colorblind users are likely to be able to see that the text is lighter, even if they cannot make out the specific color, particularly if the color used isn't red or green.
Sure, you could make links bold, but no one does that for a reason: it looks ridiculous.
The thing that I find particularly egregious about that rule about it is how this doesn't even seem like it helps that many people. A screen reader user would necessarily know that an element was a link regardless of color, and even colorblind users are likely to be able to see that the text is lighter, even if they cannot make out the specific color, particularly if the color used isn't red or green.