Aarch64 obviously isn't a completely clean sheet design. It was constrained by having to execute on the same CPU pipelines as 32 bit code, at least for the firs

Aarch64 obviously isn't a completely clean sheet design. It was constrained by having to execute on the same CPU pipelines as 32 bit code, at least for the first decade or so. And the 32 bit mode has to perform well. There are tens of millions of Raspberry Pi 3s and 4s (and later model Pi 2s) which have 64 bit CPUs but have never seen a 64 bit instruction in their lives. Android phones have been supporting both 32 and 64 bit apps for a long time. The "by people who know what they are doing" thing is just pure FUD. Sure, ARM employs some competent people, but no more so than IBM, Intel, AMD or the various members of RISC-V International.