I disagree, in the same way that I consider Firefox to be the best browser: because it is freely modifiable. So, you can make it the best for you, which is invaluable.
The fact that some distros are great for most people out of the box is just an extra perk for me, it's not that important. I could never make Windows as good as I made my Debian, or Chrome as good as I made my Firefox.
I never said they were all the same. Given a specific need / situation, I'm sure one OS will be better fit than the others.
Ie : serving web content, playing AAA games (although it might change soon), and so on.
Regarding your point on distros, I think it is, excuse me, a bit off :
while you certainly are an advanced Linux user, you need to keep in mind most of the computer userbase will certainly not be as confident as you to install tricky packages in CLI .
The UI is there to ease your work, not to hinder you, especially when you are part of the 90% of users which consider a computer as nothing but a tool.
The fact that some distros are great for most people out of the box is just an extra perk for me, it's not that important. I could never make Windows as good as I made my Debian, or Chrome as good as I made my Firefox.