For your product, side project, personal site, whatever.
Even if AI is speeding up building whatever you want, which it probably is, I hope you take some time to style it yourself. I don't care if it looks messy, or weird, or things aren't perfect. That just means I'm more likely to stay and look around a bit.
CSS is quirky by nature. Writing it can be a slog. But playing with it to get things a little more like what you imagine in your head or on paper helps. It's fun to get past the default Claude design color palette, and every little thing being in a card. It's fun to incrementally watch a page get less and less terrible.
If you're not writing CSS and your page is clearly AI designed I'll likely bounce, and I doubt I'm the only one.