TAILWIND CSS in serious apps — what I found after asking AI, using v0, and digging through GitHub

I have never worked in a serious environment, but I wanted to make sure I am doing things the way real production apps are built. So I went looking for the truth about Tailwind CSS in serious apps. I started by asking AI to help me set up my CSS foundation. It gave me a massive file — 50 variables, shadow tokens, color ramps, animated gradients, dark mode, the whole thing. Looked impressive. Felt overwhelming. Then I tried v0. Same story. Huge file, tons of tokens I never asked for, things I will probably never use. So I went to GitHub and started opening repos with hundreds of stars — real apps, real developers, real production code. Almost every single one had this as their entire Tailwind setup: @tailwind base; @tailwind components; @tailwind utilities; Some had no CSS file at all. Everything else was just Tailwind classes written directly in components. No design system file. No 50 variables. Just utility classes where they're needed. So my question to people who actually ship thin