Can you give an example where you get tripped up for months? I honestly don't understand. All the tools I use seem to look and behave 100% identical after an up

Can you give an example where you get tripped up for months? I honestly don't understand. All the tools I use seem to look and behave 100% identical after an upgrade. I don't use much Apple software so maybe that explains this difference in perception..? I think they only change that ever bothered me was when scroll bars started to disappear and stop looking uniform. That was a long time ago though, maybe before even OS X.