Adobe (ex-Macromedia) Flash is a core technology of today's Web. Unfortunately, it got a wrong start back in the days. Many designers sold their souls to the unprecedented opportunities offered by graphical web and forgot that Flash is a complement to HTML, not - a replacement. This confussion ended us in the initial flood of all-Flash websites - a complete nightmare, by any reasonable standards.
You might remember that even some big media companies made the mistake. I will spare their good names, considering that they [relatively] quickly corrected the mistake, but to make a point - the confusion did not infect only amateur designers. Unfortunately, the cure was not any less damaging - many websites and designers refused to use Flash, at all. It also helped that right at the time, Ajax emerged, giving buzzers new "hot" thing to buzz about.