No, he just wanted light to be default, not to lose the option for dark - unless I’m misunderstanding. He wants variations options but change the default from system to light.
Without in addon you need to add html to PAGE_CONTAINER template.
I added it just below the copyright line
<xf:if contentcheck="true">
<div class="p-footer-debug">
Or you could pit it above the copyright line
<xf:if contentcheck="true">
<div class="p-footer-copyright">...
That isn’t possible in the core xenForo. I just made it against the rules. If someone does it in a way that misleads, ie changes the meaning of what someone said, then I would give them a warning which could lead to a ban if they repeat offend.
Otherwise normal editing that is for brevity or...
I doubt they will find a theme that everyone is happy with. You just cannot please everyone. Point being it should be easily customisable. Which if 2.3 is anything to go by it will be.
But you don't need to with 2.3, when you use variations, because the default is to go with user's system settings. IMO this is one of the best things about 2.3