I wonder if there is a difference in accuracy of emulation. Even back in 2000 ZSNES ran smooth for the vast majority of games. The exception were games with special chips on the cartridge like SuperFX.
It's relatively easy to get the first 90%, but each 1% after that doubles the difficulty. This is especially true on older machines where the code tended to be hand-written assembly. When working with modernish machines where there's a SDK for C/C++, high level emulation tends to be much easier to accomplish-- and this is why there wasn't anything even remotely resembling accurate for N64 until the last few years. It was only feasible recently.
Gamecube, Wii, Switch, X360, PS3, PS4 -- these are machines that will remain HLE for a long time. Cycle accuracy will be arduous and require CPU resources we likely won't have for a long while.