Do HTML5 and CSS are better off without Adobe Flash? Why or why not?

Question

--Reading about New in HTML5 under HTML course--
I've kinda heard that Adobe Flash will be losing support soon, and it was said that it has something to do with HTML5 and CSS and also security, but I quite don't understand it. Doesn't Flash makes websites interactive?
And another question: is Adobe Flash an example of an integrated API? If not, then what is an integrated API?

Answer 1

://They are better without Adobe Flash plugin too, but some tag like <video>, <audio > won't be much interactive