Animation and sounds are distracting.
How can anyone concentrate on reading what's on your website when there are things flying around the page? It's like trying to read a newspaper when someone's poking you in the shoulder repeatedly.
Visitors who have slow connections may resent that you've wasted their time by forcing them to load animations and sound files. Readers who are assaulted by blinking are more likely to leave your website immediately without clicking on anything, and are far less likely to bookmark the website, return to it, link to it, and recommend it.
Always, always keep your visitors' interests in mind. Don't design your website for you, design it for the people who will actually use it.
But there is definitely a place for animation and sound - just make sure that it enhances why and what your visitor came to your website for e.g. training, trials, explanations. If you are unsure, ask an acquaintance and watch their reaction carefully (they may not say what they think) as they open your website and it's pages.