No. There are only so many apps one needs. This is a flimsy argument.
Neither is the Android you use on your phone. It uses proprietary Google code. AOSP is open source. Which is why after installing a custom rom, you need to install gApps separately.
Unlocking bootloader requires factory reset and allows you the ability to get root read/write access. Enabling developer options is something else entirely.
Many manufacturers void warranty or remove proprietary code if you unlock bootloader - examples are plenty - Motorola, HTC (s-off, s-on, yada yada), Sony removes the BIONZ DRM from their phones if you unlock bootloader - makes their camera processing worse. You can simply google and find out more examples. Manufacturers don't want the average idiot playing around with system access - which is why they offer unlocked bootloader phones separately.
Yes. Apps that allow you to customize Android at a system level - not necessary for the average user.
Again, not the average user. Even Apple gives development certs to professional developers to give them extra functionality.
That's the company's fault isn't it? To make an extra buck, they shovel crapware to their users. You don't get it do you? The average user should NOT have to deal with rooting to get basic functionality back in their phones!
Most ROMS (in my experience during Android tinkering times) are only supported so well for so long before they're abandoned. Many have small bugs and quirks which is not worth the time. Again - something the average consumer does not and should not need to do. If android manufacturers stopped churning out too many phones with crappy support that barely lasts 2 years, there wouldn't be a problem.
Apple, on the other hand, supports it's phones for at least 4 years. The iPhone 5 was still getting updates till last year.
Design & Aesthetics choice is personal and subjective.