I don't think thread prioritization is the cause of the apparent lag. We've gone from mostly synchronous systems to highly asynchronous systems. Typing on a keyboard used to be a hardware interrupt that would also print instantly on the screen. Now it's a serial bus being polled every few milliseconds, followed by a buffer copy between kernel and user space, with a/several memory allocation and transfer of ownership to a GUI thread, that when scheduled may draw the character on the screen using a DOM that needs to be recalculated which requires accessing the memory allocator in the OS which is currently locked by your Android build.