i once (~15 years ago) worked at a web design shop where the founders were both architects. they did everything in flash as it somewhat resembled the tools they knew - cad software. one of them was the designer and he was really good and they made amazing websites without even knowing a shred of html or even programming languages (they didn't even use actionscript). in case the customer wanted a guestbook they used a free ad-supported one (until i joined as a programmer).

flash was a good tool for the websites they used to create, usually graphics and animation heavy websites low on interactivity. they used the export function to generate the swf including the html index page to embed it.

over the years focus shifted more and more to dynamic websites with content generated from databases and they were mostly lost there. dynamic content (loaded by http requests from databases) in flash usually turned into a huge pain in the ass after a while. for those projects we switched to a traditional website model where dynamic content mostly wasn't loaded into flash, instead it was a html-by-php website where flash animations replaced header jpegs (i.e. animated passive content).

so, in our case, flash was a good replacement for animated and slightly interactive but not dynamically generated content.