"Apple is the only company designing chips that go toe to toe with Intel's and AMD's best" This is not a clear cut statement. ARM is not seeing much success on PC's because PC's are typically using Windows and Windows for ARM is a s***show. Secondly, where companies are building high performance ARM chips, say for data centers (AWS
Graviton) or for super computers (Fujitsi
Fugaku) they are doing ground breaking things. ARM isn't dominating on Windows because Windows is completely tied to x86 and relies on x86 programs going back decades, until Microsoft gets serious it's always going to be stuck on x86. You only need to look at benchmarks between Apple's M1 and x86 based Macs, it's a brutal wakeup call for Intel and Microsoft.
"Qualcomm, Samsung, NVIDIA, Google, MediaTek, AWS, Ampere, etc. are just using Arm's designs" Qualcomm, Samsung, Google, AWS are all building custom ARM chips now using the ARM ISA, most have perpetual licenses which is something you only do if you are serious about future development. Nvidia is BUYING ARM which signals just how serious they are. Ampere? Are you referring to Nvidia's GPU uArch - I don't know what that has to do with ARM? MediaTek will probably start building their own custom silicon as they push up the value chain but they are a budget chip company.
Your last statement is correct, being able to customize your design whilst being compatible is a big part of the appeal of ARM. But the x86 killers are here and in operation. M1 Max, A64FX 48C, upcoming Graviton3. You just aren't seeing it in the consumer PC space because Microsoft is stuck treading water with x86. The data center space is the most important area to look out for, they have regular turn over of chips, long development road maps, immense budgets, typically run platform agnostic code, and above all perf/watt is king.