Yes, I love the Harry Potter series, but quidditch is badly designed. In her attempt to give Harry a good opportunity to shine, Rowling made all players almost irrelevant except for one player in each team. I think Rowling belatedly realized this, and made an effort to show a match where the seeker doesn't win the game (even though that requires the rest of the teams to be ridiculously mismatched, so that a huge difference in goals can be accumulated).

The fact that a match can last from a few seconds to months is also a bad thing. Imagine paying to see the World Cup final and it's over in ten seconds. Or imagine paying to see it and having to leave because it just doesn't end and you have a life and work to go back to.

The previous problems could have been avoided with some slight tinkering with the rules. But there's another, more philosophical problem: quidditch is basically two different games going on at the same time: the chasers and goalkeepers playing one game, and the seekers playing a different one. That's not how a good team sport is designed: you want to have all your team cooperating and working together, not just a couple of them doing their own thing.