When I first started in web design things were different. We only need to worry about HTML 4 and 2 browsers. We concentrated on quality of the content as that was pretty much all there easy. Content was front an centre.
Then flash came along. Suddenly we had a way to integrate really rich media and interaction in out web pages. With a tiny download, we could have cross platform compatible sites, that look the same in any browser and would deliver the same experience to all.
Then Steve jobs decided that Flash was bad and suddenly everyone jumped on his shity band wagon and started to get rid of flash. Instead they created a new version of HTML (because XHTML was too hard for them to follow) and instead of having to just download a tiny plugin, you had to totally change your browser to get things working.