What the frickity frack am I supposed to do about tanks

The fact is, lethality just isnt cutting it for me. It seems as if most games come down to who has the better tanks. Tanks are now not only taking almost no damage, but are also dealing considerable damage, being great frontlines, and not letting you reach backlines because of hard cc, meaning you can't get on their squishies and can't do anything about the tanks before the carries kill you. In the picture provided, mundo deals % hp damage, facetanks, and has more than enough cc to outrun/chase any of us, since he outdamages us thanks to tankiness. Nunu does the same thing, but has a slow on his E that may as well be a root, along with providing movement and attack speed, and has a free heal in his Q.

And It's really driving me nuts. What am I supposed to do when tanks deal the most damage in the game, have the most cc in the game, and take the most damage in the game?