In practice, none of the free OSes are ready for 21st century, battery-powered, energy-saving devices, especially of the kind Apple makes.
I'm pretty sure battery performance would drop significantly if root was too easy to achieve. The temptation to run "that one more background service" would be far too much for most apps, both free and otherwise.
To get good battery perf out of a device, you need to be extremely good at saying "no", even if that "no" comes at the expense of user freedom and features. Free software is usually extremely bad at this by design, although there are exceptions (Graphene OS comes to mind).
On Apple devices, core system services are written by Apple itself. That puts pressure on the software development side to care about battery perf, as that is what users want (and what increases sales). If software is written by 3rd parties with their own business goals unrelated to device sales, I'm afraid "featuritis" and lower development costs would win out over efficiency, as it usually does in such circumstances.