It was a 3gig PSD file. That is pretty impressive.
I'm not saying it's not hard: it is hard. Programming is hard. Making sure you're not occupying the UI thread for more than 16 milliseconds per frame is sometimes a challenge. You have to use all sorts of scary stuff like "concurrency" and "threads" and "GPUs". But it's 2018: non-laggy UI's should be the baseline everywhere, for everything.
Apples and Oranges.
My Amiga never did this because the whole user interface was interrupt driven, it wasn't possible for any of the bloated trash running to deem itself more important.