Can't say I blame him: imagine building incredible silicon and hardware systems to have increasingly buggy, flaccid UX, and run of the mill SW put on top, but then locked down to the point they can't run anything else.
The notable exception is MLX, which I actually think is an incredible system and very well thought out and executed, but iOS/iPadOS/macOS, despite having the very loyal installed base (who likely thinks all is well in the world and they are just fine and always will, and, really, that's fine, I'm not saying they shouldn't feel that way if they _really_ feel that way and aren't just "coping"), looking at this from Johny et al's perspective, who likely have enough vested stock & career arc fulfilled, so "building cool things that do cool things" is probably the currency that matters the most, why wouldn't pastures at NVIDIA, Qualcomm, or even a startup where they'd get the full stack or close to it look better (where they'd also, arguably, get some diversity in their portfolio with some equity from other parts of the market)? Of course it would.
The Neural Engine is walled off, anything past M2 won't even boot Linux (and M2/M1 don't very reliably run it as a daily driver), and MLX is great but it's still not close to critical mass, and macOS/iOS/iPadOS is increasingly flat and buggy with poor UX to many people (the latter, of course, is subjective, the former is more objective), yeah, no surprise people are leaving.