If you done anything with the development of the default DE, say 2010 - 2017, and try to keep it going, and so on, you can say you helped Ubuntu. But, if you’ve concentrated solely on Kubuntu, there wasn’t much help. (Nothing personal!)
Ubuntu was made by a company, and to stay in the business, it has to spend money. By helping other remixes to come through, the company and the leader had helped the open-source world. But, the money was lost, and the idea was lost. And, most importantly, the enthusiasm is gone.
Enthusiasm is the life-blood, once it s drained, it can’t be brought back that easily.
At the beginning I liked when the remixes were embraced as official derivatives. Later, I saw the fragmentation coming in. The (free) users, went on to attack the company’s ideas of introducing new thoughts. And, so on…Those who stayed with Ubuntu from the beginning know that.
Fragmentation is the problem. Your own Kubuntu has a competitor in KDE Neon.
Flavours cannot be removed. Simply because, they are already there. Going back through the last decade, one can say that flavours shouldn’t have happened. If Kubuntu had been a remix from the beginning for example, its creator wouldn’t have to move out to create KDE Neon, just maybe. It is history now.
(I also have a KDE Plasma install btw, neither Kubuntu nor Neon, but OpenSuse Tumbleweed. I had both, but dropped them and went back to the old friend. Very good wiki.)