4.9% of Websites Use Flash, Down From 28.5% in 2011 (bleepingcomputer.com)
Web makers continue to ditch the infamous Flash for other safer, improved technologies. In 2011, more than 28.5 percent of websites used Flash in their code, a figure technology survey site W3Techs estimates to have dropped to 4.9 percent today. BleepingComputer: The number confirms Flash's decline, and a reason why Adobe has decided to retire the technology at the end of 2020. A decline from 28.5 percent to 4.9 percent doesn't look that bad, but we're talking about all Internet sites, not just a small portion of Top 10,000 or Top 1 Million sites. Taking into account the sheer number of abandoned sites on today's Internet, the decline is quite considerable, and W3Techs' findings confirm similar statistics put out by a Google security engineer in February.
Once technology breaks the 1% market share. It will take a lot of effort to actually kill such technology.
They are still people making programs and hardware for the Commodore 64 and other vintage systems such as Apple ][.
The main rule of thumb, if you are making a new site, don't use flash, if you expect the general public to use your existing site, replace flash. However if your site, wasn't flash users, who has flash on Virtual Machines, or legacy systems. Then they will keep it.
If something is so important that you feel the need to post it on the internet... It probably isn't that important.