I thought that too but it’s come on leaps and bounds in the last year or so, with the 2 links I posted you can pretty much add anything into the customizer… It’s not perfect but it’s being worked on pretty much all the time by Justin Tadlock so it’s only going to get better.
The beauty of the customizer over redux is the customizer is a preview panel, so they can see the changes before the save, so they can see the colours change and test the options before they save it.
Redux can save to the customizer as I said but imho redux just becomes an extra script you need to update. The customizer is the future 