People are absolutely part of an ISA's ecosystem. The ISA is the interface between code and CPU, but the code is generally emitted by compilers, and executed in the context of runtimes and operating systems, all designed by people and ultimately dependent on their knowledge of and engagement with the ISA. And for hot code in high-performance applications, people will still be writing directly in assembler directly to the ISA.

ISA != ISAs ecosystem

ISA is just ISA

But you get the Environment for free if you choose the ISA, so ISA=>ISA ecosystem. It really does matter when making a decision