The Harpoons are still as advanced as anything out there.
There is no firm evidence that China has got the SS-N-26.It’s probably building it’s own supersonic missiles.
Mach 2.5 provides many advantages to an ASCM, all other things being equal. The Soviets-Russians have poured tremendous R&D into ASCMs to make up for their lack of aircraft carriers. IMHO, they have the best ASCMs in the world.