Iffix, I'd like to propose a workaround for you.
Though you can't completely shut off the ranking system, there already exists a method of play that largely ignores it.
Play training games instead of online games. You could create a new account such as Iffixreboot, or Iffixreborn - or any other name that catches your fancy and play only training games.
Win or loose, training games do not affect your ratings. They also cost less to play than online games cost. Now, after a few weeks, or a month, I don't remember which, your "rating" would begin to loose 5 points, If this decay bothered you, you could again create a new account. You could do this every 3 or 4 weeks - however much time it takes til the decay would kick in. In this way you could play whichever games you enjoy and not have to bother with the ranking system.
I don't know if there is a way to delete an old account. Admin would know better than I do. But if it's possible to delete an old account, you could possibly do that and even keep you current name.
In any event, if you do enjoy the site and the lovely games this could be a way for you to play in a way that gives you pleasure and avoids the part that
"has sucked all of the joy" out of your gaming experience.
Good luck in whatever you choose.