Well, today I spent a lot of time waiting for some slow software that I wrote and maintain, a program that helps ship large desktop apps that use JVM or Electron. It can do native apps too but nearly nobody writes those. So I guess I both feel and create your pain in several directions.
Why is my software slow? Partly because the task is inherently intensive. Partly because I use an old Intel MacBook that throttles itself like crazy after too much CPU load is applied. Partly because I'm testing on Windows which has very slow file I/O and so any app that does lots of file I/O suffers. And partly because it's a JVM app which doesn't use any startup time optimizations.
But mostly it's because nobody seems to care. People complain to me about various things, performance isn't one of them. Why don't I fix it anyway? Because my time is super limited and there's always a higher priority. Bug fixes come first, features second, optimizations last. They just don't matter. Also: optimizations that increase the risk of bugs are a bad idea, because people forgive poor performance but not bugs, so even doing an optimization at all can be a bad idea.
Over the years hardware gave us much better performance and we chose to spend all of it on things like features, reducing the bug count, upping complexity (especially visual), simplifying deployment, portability, running software over the network, thin laptops and other nice things that we didn't have on Windows 98. Maybe AI will reduce the cost of software enough that performance becomes more of a priority, but probably not. We'll just spend it all on more features and bug fixes.