I want the freedom to install the OS I want on my phone. Now if I install a proprietary OS, I get what the developers of that proprietary OS choose to do. And if that proprietary OS does not give me root access, well, that's life.
Of course you do. You can run GrapheneOS, or LineageOS, postmarketOS, or mobian, or many others. All of those are open source, you can modify them as you want before you flash them.
What is your goalpost for a "serious OS"?
What market share proves is popularity. Which is important in an OS, but ridiculing other people's choices on grounds of market share doesn't seem very convincing to me.
Doesn't make you right. PostmarketOS and LineageOS are very much NOT the same OS in a different shirt.
Don't try to be provocative just because you were wrong, it doesn't help.
And that I disagree with all the whining about having root everywhere. If you are able to install your preferred OS on the device you own, then you can install one that has root, or fork an open source one and add root, or write your own.
Stop expecting differently.
Probably your problem is that you have no phones, only someone's thin clients.
Did people used to get like this about pocket calculators or digital watches? “Why am I forced to be limited to only the manufacturer’s firmware?”
I guess it is more debatable for a pocket calculator or a digital watch, but IMO when I buy a smartphone, it should not be illegal for me to install whatever I want on it. And the manufacturer should not add technical measures to prevent me from doing it.
That does NOT mean that the manufacturer should implement the features I want (like root access) or go out of their way to give me tools to install my favourite OS. Just that they should not prevent me from doing it (say if I manage to reverse engineer the hardware). Because I own the hardware I buy. At least I should.
If I buy a device, I want to be able to install whatever I want on it, and I want it to be legal for somebody else to sell something that I can run on it.