I also like old carburetors and simple electronics, but we're in the vast, vast minority. Most people want a car they don't have to think about or understand, looks pretty, and will take it to a shop when something goes wrong.
Gentoo is quite a bit more work to get set up than other distros, but
* Once you get it set up, it just keeps on going
* If you're already fairly familiar with Linux system administration, the setup process isn't hard... it just involves a lot of waiting, unless you use the distro-provided precompiled packages
* There's really good documentation that walks you through the installation process and leaves you with a computer with a functioning bootloader and kernel, Internet access, and some pointers towards what you might want to install next
Networking protocols, connections, error states, etc are inherently complex and require equally sophisticated handling that linux may not always do. Some software chooses not to handle at all and expose directly to the user - but others like KDE simply lack the millions of dev-hours of polish that Windows and Mac have.
As for KDE polish, the only reason that’s true is because of someone’s choice to not put energy toward that part of the desktop.
Linux needs polish for sure, but given a finite amount of time, energy, and money the reasons are likely more complicated than "they don't care"
While /technically/ still true, I lament that it is increasingly inapplicable to the world around us today.