Unfortunately, none of these are responsible for the startup delay. Since version 1.18 effectively ~90% of the startup duration is spent starting up WinUI and having it draw the tab bar and window frame. It still needs a second to start. If it still used GDI like Windows NT did, it would start in well under 100ms even on an extremely old CPU.

Fixing this situation is essentially impossible because it requires rewriting almost everything that modern Windows is built on. Someone else in this thread said you couldn't sell 4 quarters worth of work to fix this, but the reality is that it requires infinite quarters, because it requires throwing away the last 10 years of Windows shell and UI work and that will never happen. You could paper over it by applying performance spotfixes here and there, but it'll never go back to how it could be that way. At a minimum, you'd essentially have to throw away WinRT which has an almost viral negative impact on performance. Never before have high latency, but still synchronous cross process RPCs been that prevalent and everything's a heap allocated object, even if it's within the same binary. It's JuniorFootgunRT.