Is it though?
Obviously all processors are designed for their market and until recently for ARM that has mean phones and tablets where ARM have done really. And Apple (who only licence the ARM instruction set) have by most metrics done exceptionally well - naturally at the kind of things a phone or table can run. But the benchmarks for the iPad Pro are pretty impressive with single-core up there with the best Intel and AMD can offer while using 5W or so.
This doesn't meant they can scale up to 15W, 25W, 35W or so. However, Apple design team is very good, and the other recent ARM news is that the world's fastest supercomputer is now the Fujitsu Fugaky and that's totally ARM without any GPUs:
https://www.anandtech.com/show/15869...-415-petaflops
At that scale, Fujitsu obviously used their experience to have build the buses and memory system so it is not really comparable to a phone SOC. ARM just gives vendors the freedom to licence whatever they need and customise it.