My pick would be, dealing with the ‘wild west’ atmosphere. That being, before cyber bullying laws existed, you had bunches of people getting off scot-free with telling you to off yourself or call you a list of derogatory terms.
Today, Flash can be played using a browser extension, written in Rust, that translates the Flash code into WebAssembly (Wasm). This can also be embedded in a web site; this is used by e.g. https://homestarrunner.com to play old toons & games.