[onion2k]

Just seeing the skeleton of the web page doesn't make it fast.

I didn't say it does. Skeleton loading is slower. It feels faster though, and that perceptive improvement is more important than the actual time something takes. If you ask users which they think is faster they usually say the skeleton version regardless of the facts. When your key metric is user satisfaction rather than raw download speed that's important.

The page will be unresponsive for longer and will visually stutter while rendering.

That doesn't have to be the case though. There are plenty of techniques for writing client side code that doesn't block user interaction.