You can check the contrast ratio between the colors. According to WCAG, the minimum contrast ratio for text and background should be 4.5:1, except for large text, where it can be 3:1. This will improve accessibility and make sure people can read the text on your page.
You can test the contrast ratio from your color on this page: https://contrast-ratio.com/
I don't think any increase or reduction in the number of breakpoints would be achieved using aspect-ratio. So no disadvantages and the advantage is only if it makes more sense to you while developing. It is a less used approach but not a bad one as long as you couple it, as you mentioned, with a screen pixel-size. The pixel size would be used to render a ...
I think it's all about well designed, curated and developed design system.
line-height is correlated with typography.
Example this dribbble picture.
In .scss preprocessors it's possible to define variables
(developers, usually do more intelligent/complex issues than styling
so this may be the mess you mentioned)
It's possible to define line-height on a ...