The CSS for the site is, and has always been, a huge, overcomplicated mess. There are some variables set up to aid with colour consistency but so much of it has been individually styled as I've made changes and additions.
Dark mode adds a fair chunk (duplicating some of that overly complex structure) and it would be nice to use the new light-dark() CSS function but, as is the way with new, browser support isn't there yet. I made a version of my CSS using light-dark() to test the impact and managed to remove over 200 lines from the file.
Like Dave Rupert I could wrap things in @supports checks but would need to heavily streamline the CSS before that would be viable.
At some point I'm just going to have to bite the bullet and try to tidy it all up and simplify the site layout. There are a few places where I use grids but things could definitely be improved as there is so much manual spacing to get things aligned.
