How do you deal with flurries and aggressive bum-rushes?

Most beginners tend to charge forward wildly to overwhelm their opponent. They abandon technique and just start swinging, hoping to land something big or score a lucky knockout.

What’s the best way to counter this? It feels difficult to respond cleanly in the middle of all those rapid strikes. Should I focus on blocking the first shots and then pivot out? Or just let them punch themselves out until they tire?

Also, I rarely see professionals using wild rushes like that — why is that?