The tweet mentions that you could 'just' send an SWF file to someone and it played. Well, if anybody had to fix a computer, or hosted anything Flash-based during that era, then they would know that's bullshit. Sure maybe with the standalone Flash player it worked allright, but that's not how people really used Flash. Even in my experience, a single SWF running locally didn't always work across all versions of Flash player.
Flash on the web only worked if you had Flash player plugin installed. Both browser and Flash updates themselves would break the Flash plugin constantly. That was across all browsers and platforms. Keeping plugins updated and reliable was a mess, for a long time there weren't even auto updates.
Flash was a mess the whole time. Let's not pretend that it ever really "just worked" because it didn't.