Flash sites were creative, in that they were occasionally built by people with amazing talent and great skill.

Most of the time, though, Flash was the multimedia CD-ROM of the web. Flash was an extension shoehorned in, didn't feel like the rest of the web, and didn't deeply integrate with the browsing experience.

Flash content was an alien rectangle, a wormhole into a strange dimension, where a mouse click would often not behave anything like a mouse click usually would.

Flash pretended to be on the web, but Flash was not of the web. That's why it's now gone.