In most reasonably-sized websites, Tailwind will decrease overall bundle size when compared to other ways of writing CSS. Which is less code, 100 instances of "margin-left: 8px" or 100 instances of "ml-2" (and a single definition for ml-2)? Tailwind will dead-code eliminate all rules you're not using.
In typical production environments tailwind is only around 10kb[1].
[1]: https://v3.tailwindcss.com/docs/optimizing-for-production