Well the 3 rule for most new/reworked champs.
Low CD on everything, that can't stop an ult, or an ult. itself.
High mobility, or tank.
Low costs, or no cost.
High damage (generally on everything).
I wrote MOST, because Pantheon, and Kayle are exceptions for now.
Low CD means, that there is no opening. He uses all the skills, and. Nothing. You don't have time to abuse it, and counterattack. By the time you can do anything relevant everything is up again.
High mobility makes them hard to target, and gives them the power to decide when to fight. You can't outrun them for escape, or reach them for engage. Even worse when a champion can escape without going all-in. Those champs just jump on you, deal damage, then leave. Whether you are dead or not.
Low costs+high damage erased the "build defense" outplay method. Back in the day one of the outplay was to build defense, and farm under turret. You might not be able to defeat the opponent, but at least can survive, and farm. Now that doesn't work. You can put all your money on defense, and still get killed quite fast. And if you are forced to recall, then plates gives extra gold to opponent.
With Xerath "support" botlane is kinda auto win. Unless enemy is a freaking dodge-master. I'm not good with it. Less than 10 games, but on every single one we won lane phase. Even if just 1 from 5 Q hits is more, than enough to force recall, or kill. Not 4 from 5, or at least half. 20% is enough.