Oh, to return to what life was like 23 years ago, when GUI applications were so simple that you could get away with fitting all their work onto a single thread.

Nowadays, a great many GUI apps have a lot of data crunching to do in the background. You've really got two options for how to handle that:

  1. Be intermittently unresponsive, like iTunes.

  2. Do work on a background thread, like decent software.

(Intentionally omitting the option of breaking your work into a bunch of tiny bits that can be handled on a single thread's event queue like some sort of deranged node.js app from hell, on the grounds that please no I can't even.)