And there was a point in... 3, I think, where Harry was instructed to delay catching the snitch until they were at least 50 points up because they wouldn't have enough league points or something to progress if he didn't.
I mean in the books the matches typically score somewhere of 5-10 goals per team until Harry catches the snitch. So it is pretty much the catcher of the snitch gets to win the game.
Maybe we can give the benefit of the doubt that snitches used to be harder to catch before brooms became crazy fast and agile like the Nimbus and Firebolt series. It is mentioned that there were matches lasting for days, but in the book conveniently the matches never seem to last more than two hours or so.
Could be, we know from 7 that they're bespoke for every match for catch dispute reasons, the artisans could probably tweak them to match a school league. That said, I don't believe Rowling put this much thought into it.