Before the"locked devices, people had the inverse problem:
everything was two open ended and complicated, could cripple the system, stuff was open for exploit (much more so than in this case of unpatched vulnerability, viruses were everyday occurence). Techies didn't have this issue, but the general public did (heck, even techies did suffer somewhat). And that might have been OK for when the PC was an unconnected tool, but not when everybody has one with them, from school to nursing home, and everybody buys and does tons of sensitive stuff from it, while connected 24/7.
Whereas you can give a 2-year old an iPad, and they can start using it just fine...
Back in ‘the old days’ (80s+90s), a child with access to a computer was likely to learn something, even if their primary use of it was playing games.
Every been to the modern web? Or used 90s-00s shareware?
Compared to those, the iPad is advertising and nagging free...
And can be totally free, you don't have to buy (a) adware apps, or (b) games with in-app-purchases.
I only get stuff that's in neither category, which all the best apps are...
What makes you think that if Apple would provide a mechanism in iOS, like SIP (System Integrity Protection) on macOS which can be disabled by technical users if needed, would change anything?
Right now, regular users do not disable SIP on macOS so there's no issue there. They don't even know/care that this possibility exists. So your 2 year old could still use the same iPad just fine.
That's because this new devices aren't "secure" but severely limited and crippled, you can't do much with them and they are far from actually usable like a computer. By that metric, my old Nokia was even more secured than an iPhone.
That's the whole point: for them to not be as open ended and complex as computers, while having the power to run highly feature-full apps.
>By that metric, my old Nokia was even more secured than an iPhone.
It indeed was, and that's the ideal. To make extremely feature full modern smartphones as easy to use and as complexity/trouble-free as appliances...
Maybe on Windows, but on macOS this has never been generally a problem.