Have you tried turning animations off? The setting should be in the Accessibility section somewhere. When you open an app from the app drawer, there is that lit

Have you tried turning animations off? The setting should be in the Accessibility section somewhere. When you open an app from the app drawer, there is that little animation where the app icon grows, the screen fades to white/black, and then the app display fades into view, which all adds up to about 100-500ms. If you disable the animation it should open almost instantly.