Earlier quoted context omitted.
Flash was not an essential part of the web in 2012. Maybe, if you had some weird work tool you had to use, some video players on the web but that was mostly it. In 2012 flash for Android was killed and it was very well known that it was going out of the window in the near future.
Many video players were still using flash. VKontakte still had its flash app/game platform going strong, though you did have the option of using an iframe that loaded a web app from your server instead. Flash support was only discontinued there around several years ago.
Flash was almost certainly not an essential part of the web. 2012 was 5 years after the iPhone and by then Android and iPhone constituted the majority of web browsing, and neither supported flash at all.
You couldn't very well say something was an essential part of the web if it wasnt supported on those devices in 2012.