Solo queue winrate at your league is the only thing that matters.

You're silver and Toxic Champion With No Counterplay #1013910 has a 44% winrate in silver?

What are you even complaining about? If the enemy picks that champion, you have a very good chance to win in the end.

If you're arguing that the champion is not fun to play against, you may have a point (then again, winning is fun, and you're bloody likely to win). But claiming that the champion is overpowered simply because the champion is likely to have a good KD in lane...? Who cares about KD in lane?

• "Winrate is meaningless because the champion is only played by noobs, he's actually OP!" Well that's great! Your silver opponent who picked the champion is a noob! Enjoy stomping his face.
• "Winrate is meaningless because only people who main the champion play him, he actually sucks!" Well that's great! Your teammate who picked the champion mains him! Enjoy getting carried.
• "Winrate is meaningless because the champion has 26 dashes and 4 knockups!" Yes, and you're silver and the champion has 44% winrate in silver. Champions must have certain traits to be viable in professional play, and dashes and knockups are high on that list, but you're not in the LCS, you're in silver and your opponent is retarded and is probably going to use those dashes to towerdive you at level 3.
• "Winrate is meaningless because what if the champion is on lots of teams with leavers?" It evens out over the course of 20 million matches. And if people do tend to leave a lot in the presence of said champion for whatever reason (toxic fanbase, selfish playstyle) then congratulations! The enemy team is now more likely to have a leaver!
• "Winrate is meaningless because I'm playing only one match, not 20 million!" -facepalm- That's like saying the next car passing by is equally likely to be a Veyron or a Camry because they're both cars.
• "In the latest LCS the champion was picked 106% of the time! He's clearly OP!" You're not in the LCS and crucially your opponent isn't either. You're in silver and the champion has a 44% winrate in silver. This probably indicates that people in silver can't play him. Which means your opponent can't play him. Go make him cry.
• "Winrate is useless because what if the enemy team picks a 44% winrate champion and a 56% winrate champion?" No matter what they pick, the 44% winrate champion is going to weigh them down in some way.

A champion's winrate at your division is the aggregate of every factor that affects the effectiveness of the champion: its actual power, its toxicity, the intelligence of its players, the morale impact of a perceived strong/weak champion, etc.

Winrate doesn't pretend to tell you just why a champion has 44% chance to win in your league, only that he does. Perhaps the champion is actually insanely overpowered but the gods hate him and people who pick him are more likely to get hit by a meteor. Doesn't matter. If the enemy team picks the champion, there is a good chance they get hit by a meteor and you win. Stats don't lie.

Tl;dr The only champions you should worry about are the ones with a high winrate (in your league!!!) because all that matters is winning.

Inb4 downvotes by people who don't understand