But pure Javascript in itself is rarely the problem, there’s plenty of CPU-demanding websites that are responsive and performant. IMO the problem is what JS en

But pure Javascript in itself is rarely the problem, there’s plenty of CPU-demanding websites that are responsive and performant. IMO the problem is what JS enables: making lots of very slow Ajax calls for every small interaction. Which works great in development machines but sucks when a real network is involved. But your point stands, dropping to server-rendered HTML makes it fast again.