How do you design a progressive loading system using skeleton screens, optimistic rendering, and streaming to minimise perceived latency across all network speeds?

Imagine you're building a sandcastle. Instead of making you wait until it's completely done, I first show you the outline of the castle (skeleton screen), then I add sand bucket by bucket (streaming), and I pretend the first bucket is already a tower (optimistic rendering). This way, you feel like the castle is ready much faster, even though it's still being built.