Half the posts that turn up when you search tumblr for "quadball" are from people who say that they have never played the sport and take great delight in mocking it for its recent change from "quidditch" to "quadball", most of them saying something along the lines of "it doesn't matter if they change the name, the sport was still originally invented by JKR and she's bad and therefor nobody should play it".
It's such an obvious example of what happens 1. when people who don't know anything about a topic still have strong opinions on it, and 2. when people care more about being "on the right side" of things than actually looking into the thing.
Quadball is (with Ultimate Frisbee I think) one of the very few team sports that allows trans players to play as their stated gender, no questions asked. It allows nonbinary players to play as nonbinary. It is a mixed gender, explicitly gender inclusive sport that tries to write its rules in such a way that this works in practice, not just in theory.
So. If you care about trans people more than about being on the right side, then quadball, as it exists in our world, is a good sport, no matter its origins. If you just want something to hate, then by all means, throw one of the two or maybe three sports that are radically inclusive under the bus. But don't think you're doing anyone any favours except your own feeling of self-righteousness.
Quadball was the only sport available to me where I could play as male before I went through the (long and arduous) official procedures. All the teams I know try their best to be welcoming to and safe for trans (including nonbinary) players. In times when just existing in public was a fight, my team had my back and was one of the few spaces where I could just exist as myself, no questions asked, no need to prove my gender to anyone. This is what the people involved in it are doing with it. Either listen to us or shut up.