Ask HN: Seeing all these “overwhelmed with front-end” posts, I have a question

What do all of these front-end tools such as React, Angular, and all the other stuff people are complaining about do that good old PHP/MySQL/Javascript can't do?

Forgive my ignorance, I only know HTML/CSS and a little Javascript/PHP. I'm assuming the frustrating frameworks are used for things like SAAS apps.

But can you give me examples, hopefully with URLs, of applications that you can only build with Angular, React, etc.