How do you spin off a website so quickly ?

Hi guys, I have been working on a project with heavy backend and I am about to get on the nitty gritty of UI. I often see very one posting their stunning websites. What are you guys using ?

I am good with HTML/CSS/JS but It would take me lot of time to design something from scratch and bootstrap isn't beautiful anymore + it has lot of unwanted/unused code which just slows down pagespeed.

So I'm wondering what are you guys using ?