How much Bootstrap 4 Can help for a real world project?

Yes, I guess so, what UI kit you recommend? but I guess there are still worthy to do it (at least once) from the ground up.

It depends on the framework you using. Different frameworks have different UI Kit. Yes, it definitely worth to do from ground up, and we will realised that are so much we don't know along the way.

Thanks, Lucy. My prospect in this article is how much we can lean on a framework without using too much customization, turns out in the real world, we still need CSS.

Yep! And that makes sense. Really the biggest benefit to Bootstrap are the grid system and the built in components, like modals and that ilk.