This has been a problem for years.
Why aren't you detecting them? I've just played like 5 games in a row with 3 or more bots on my team, all basically running it down mid and going 0/15, and occasionally typing a random sentence like 'Silence.' or 'attack a tower together.' to easily fool your bot detection system.
Your game is going to lose players in the future if this is the new player experience.
It's not fun to play for 25 minutes and only get 30 xp because I had a team filled with hardfeeding bots. A company the size of Riot should have the resources to deal with & detect this better.