>by the time you have it worked out, the phone is obsolete and very few people still use it.
If you work out a phone from 5 years ago, you're not that far off from a phone of today. Nobody designs it all from scratch, you mostly modify the old one. Getting the foundations going will take years - adapting the foundation to a different phone of the same series will only take months.
Hardware is hard. It doesn’t always have the transparent composability that software has because you hit physics and the real world.
The example already given makes the point. Work has been great on the M1 but my understanding is that this has not translated all that well to e.g. M2, M3 and M4.
If you work out a phone from 5 years ago, you're not that far off from a phone of today. Nobody designs it all from scratch, you mostly modify the old one. Getting the foundations going will take years - adapting the foundation to a different phone of the same series will only take months.