If you're getting stuck with bots, it would be better to just let the enemy team push and win, and then report the bots after the game so you can help get them out of the game and so you can actually contribute something to the community instead of making these threads crying about it.
Bots are always a problem, in many, many games. A majority of them are bots that spam advertise cash-currency selling sites for games that have cash-shop features. They're not always easy to detect because it might not be a script that's interacting with the game itself, it might just even be a silly macro that is programmed to hit enter, copy/input a certain text, and press enter again at timed intervals where the game window just happens to be the active/target window. Of course the bots in league are more complex because they have to actually "play" the game, and I use the term loosely.
Riot bans these botters in waves instead of constantly and actively because constant active bans give the botters a chance to constantly and actively make changes to the script and try to pinpoint the reason as to why their programs may have been caught by Riot's detection that is outside of just being reported by others. If this happens, it would require riot to constantly be trying to keep up with constantly changing scripts. Bans in waves allow riot to get a list of botted accounts over a mild period of time and bans them all simultaneously in one go, giving script programmers/writers much less chance and feedback to work with for their use in updating and upgrading their scripts, keeping them in the dark about how to avoid detection.
If you want to leave league, go ahead. Nobody's forcing you to stay and, by the looks of your attitude honestly, I doubt you'll be missed much.