[nomilk]

Tailwind provides many classes to use right out of the box, whereas vanilla CSS requires classes to be written, which takes longer.

If someone's good at, fast at, and enjoys writing vanilla css, it might be the way to go, but if they don't have a sense of design or lack skill in writing CSS, a framework allows pages to look professional quickly.

A site made with a css framework may not be as extensible as one made with vanilla css, but if there's strong enough desire it could always be taken out and swapped for vanilla CSS.

For quickly getting things done on projects where time/resources are , I'd go for a frame work (for the reasons above: I lack a sense of design and would spend an eternity tinkering and doubting my design choices).