Teamwork based Champions
In my opinion, champions that are proficient when you're with a good team, or with friends, are not viable champions. Especially in this basket of toxins, salt, and trolls. It seems like before Kalista was released, Riot was content with releasing champions that could function by themselves, with minimal help from other players. Braum only needed an ally to dash to for ult positioning, or to increase their resistances. Yasuo only needed a knockup for his ult, which he can create himself or use someone else's knockup. Ekko doesn't need anyone, because he can rewind time and get out of sticky situations if his teammates don't follow up.
Now, we have champions that will only work properly if used in the best interests of the team. Obviously, Kalista's ult needs to have communication in order to lock down the correct target. Problem is, in solo-queue, you can't tell people who to knock up on the spot or during a teamfight. Things like that are completely reliant on the CC heavy person locking down the correct target, or pre-fight communication. WHICH IS IMPOSSIBLE, because everyone knows before teamfights, stopping to type is NEVER A GOOD IDEA. So here in lies the problem, if you're Kalista sitting in the backline, and your CC heavy support charges forward and locks down the enemy. BUT! Someone was late to the fight, and uses that as an advantage as you are the backline left to deal damage. If you ult your support, and she doesn't notice you're dying, and you can't tell her that they should peel because you're too busy using Kalista passive, then they're obviously going to rejoin the fight in the front wondering why in the world you ulted them.
Secondly, Bard! Before I say anything, let's note that he is not garbage. He is wonderfully useful IN THE RIGHT HANDS. Unfortunately, out of the 27 million people who play League of Legends, maybe only 1% know how to correctly use him. Let's face it, the problem is with his AOE Zhyonas. Are you trying to escape an enemy? Let Bard help you, and ult YOU AND ONLY YOU. That way, your final destination, will be on the end of whatever weapon the enemy team is currently holding. It's a great mechanic, great for tower diving, stopping enemies, or killing that one person who you got really fed but is still being an ass to you.
Lastly, Tahm Kench. He has a very unique kit in the fact that he gets two free abilities to kill, or hamper his teammates progress. Trying to leave base? Just get your toxic Tahm Kench to swallow you before you reach inhib tower, and carry you right back to the fountain. You also can't escape him, because he has homeguard, and moves much faster than you do. Oh, did you get CC'd by someone who will potentially kill you? Let Tahm Kench swallow you, and run right into the enemy team! That way, no matter where you get spat out, if you don't have flash you're going to die. Because let's face it, we've all had that Tahm in our game before. However, the CC negation, and the speed boost are both very useful tools, only if your Tahm is hell bent on helping the team, and not trying to screw you over. Oh, think it can't happen too often? Listen up, it's got a 10 second cooldown at max rank, plus 40% CDR, that's a six second cooldown. Meaning he can pick you up and spit you out faster than you can walk from fountain to inhib turret. Don't believe me? Here's proof.
Also, his ult. While it is a great initiation tool, it's also a great way to get yourself killed if the wrong person jumps into your mouth. Remember what Phreak said on his champion spotlight? I don't either, but it went something along the lines of, "If the wrong person jumps into your mouth during a game changing initiation, then you might as well have just lost the fight." As characterized with the example of picking Sejuani over Ezreal or Draven during that moment. Which is odd, because unless you stop to type (which takes a while) you might lose the perfect moment to engage, and be left with a much crappier, and potentially favor changing engage.
Please Riot, stop making champions that only work well with people you know and trust. Most of the people you play with ARE NOT PEOPLE YOU KNOW AND TRUST. YOU WOULD NOT TRUST THEM WITH YOUR MONEY, NOR SHOULD YOU TRUST THEM WITH YOU IN GAME LIFE. You guys are too focused on the LCS scene, where toxicity is practically non-existent, and the teamwork is present in every game. There are 27 million people playing your game, and you only focus on 410 of them? (82 professional ranked teams, estimated as 5 people per team) That just shows that you are not a player based company, and that you really have no interest in the well-being of the game. It shows that you are only focused on the Professional E-sports scene, where you make most of your money. If you really cared about us unprofessional players, then you would reply to more things on the forums, offer better reasons as to why you do things, and maybe take suggestions from the people who play the game!
If you made it down here, thanks for reading! There's no TL:DR, because this is pretty important. Anything you want to add, anything rude you wanna say, leave it below, I'll probably respond.