I mean some of them are less good than others, and the economies on them vary. Most decent ones these days though use a points system where you earn points based on how long you've seeded torrents. You use points to purchase upload credit which artificially raises your ratio. Not all of them require you to have accounts on other trackers, some of them have an interview process that after you've passed you can create an account, I'm not sure if this is what you mean by "open/effectively open". These are still private trackers, and from them you can get access to invite only trackers. There's several avenues you can take to get onto different private trackers, it's not hard it just takes time (and seeding!)