If that's what they want who am I to tell them no? The point of open software is to be what the user wants. Why is any particular opinion more correct than another within a group that prides itself on giving users choice.
If KColorPicker isn't someone's cup of tea, there is nothing stopping anyone from changing that default out. The color picker that appears is a user setting.
They're giving you shit about complaining about a nice and working color picker for no reason except that somebody made something similar quite a while ago. Nobody cares about your color picker, you are the only one bringing it up.
If it's such a problem for you, and you are obviously a colour picker expert, why don't you make KDE a new colour picker. I'm sure the community would appreciate a new and innovative colour picker, if it's genuinely better than the Windows style one.