Not to mention that early on, CSS was very lacking compared to today. We didn't even have `border-radius` until something like 2011! Consider that this relatively simple site design[1] takes about 420 lines of modern CSS[2]. And that's even using nesting, and liberal use of :has, which is a game changer. I remember having to restructure both my CSS and my HTML to achieve appearances which were otherwise impossible to create in the intuitive way, all because of inherent limitations to CSS at the time.
CSS rounded corners often looked a bit pixelated in the early days, and I remember doing image-based corners well after border-radius was widely supported.
By the time CSS rounded corners became really smooth a lot of designers had moved on to the boxy flat look, and square corners were fashionable again.
[1] https://90s.dev/
[2] https://90s.dev/style.css