To the Wolf:
My first time posting because I’ve been there before and I commiserate with you. Although you have a completely valid point, you’re in a very tough position, because refraining from reciting kaddish when one is obligated to do so appears to belittle one’s parent’s honor. Additionally, every effort should be made for the kaddish to be said in unison, even though the other mourners are showing a total disregard and disrespect to you by not slowing down to say it with you.
I personally tried to say every kaddish with the tzibur even if it meant saying it a little faster and without concentration. There were some times when I would abstain when I sensed the kaddish would be said so fast that the words would be mangled. I don’t recall being in such situations often, but I do recall wishing in my heart (and maybe even praying) that the speedy readers not partake in my minyan. Wish I could give better advice.