I’m currently going through the same issue. I’m procedurally generating my world with the Runtime Mesh Component (from a plugin), and using Async / FNonAbandonableTask to speed up the process.
Depending on how large of a world I generate, the loading time can be 3 - 15x slower in the packaged build,
I’ve attached an image from Unreal Insights, showing the time taken when running my project in the editor, compared to the packaged build
