I don't know if people still care about red white or ever cared about it? I feel like when aphelios was new there were a lot of clips of him destroying a tower 100-0 or whatever with red white, I even vaguely remember a caster saying "red white, don't fight".

The problem with red white is it might be the highest dmg to towers and dragons and target dummies, but champions tend to run away and be hard to continuously hit. This is especially pronounced for something like sona looking for short trades with good spacing - you have a lot of room to Q and maybe auto red/white with like one or zero autos in return, but very little room to do that to green/white. It's not just short trades though, even in actual fights I feel like green/white has many more chances to actually hit the target and stack his damage, and the basic ability/ult he gets has waaaaaay more range, letting him finish a low fleeing target.