I recently ported an early-2000s 2D game to WebAssembly and old Asyncify was too clunky and the Emterpreter was too slow to be useful. To get things working comfortably I ended up porting the game loops to use Clang's support for the C++ coroutines TS, with a simple scheduler that yields control back to the browser after every screen flip. I will have to see if this new Asyncify can do any better.