5ms input lag isn't a dealbreaker. Even the Apple II was around 30ms touch-to-pixel latency, limited by its ~30fps.

https://danluu.com/input-lag/

According to the above, the 2017 iPad pro with Apple Pencil replicated the Apple II's 30ms touch-to-pixel latency, four decades later! (Current M4/M5 models are supposedly 5-10ms, so perhaps a good emulator platform...)

Congratulations, Apple - seriously.