The Flash player is gone, but the authoring software called Adobe Flash was just rebranded to Adobe Animate. Back in the Flash times Flash was quite popular for Western-style 2d animation, and a lot of TV series were produced in Flash. Animate has been keeping that somewhat alive, though better alternatives have emerged.
Yeah. For all the hate the Flash player got back in the day, the authoring software (which was Macromedia Flash when I last used it) was awesome. It has really nice motion interpolation (tweening) and onion-skinning tools. For Western animation this meant you didn’t need to outsource all the in-between work.