Awhile ago he was a strong adc pick.
Then people complained he "had no counterplay" and NEEDed a nerf.
Now people complain riot shows no love to urgot.
There's a big misconception going around about this; power is not the same as counterplay. Urgot overall has low counterplay, and when he's at equal strength to other champions in his role he is absurdly frustrating to play against. He's still frustrating when he's numerically weaker, but it's less mind-numbingly terrible to face him.
Yorick is another good example. He has almost zero counterplay outside of "soak up his poke and win the duel", and when he's strong/viable it sucks to be against him. This doesn't necessarily mean he's overpowered, but he is completely anti-fun and could probably use a nerf so he doesn't continually ruin games.
One final example, Evelynn. Evelynn used to be (and somewhat still is) total bullshit. She wasn't necessarily overpowered, but the amount of frustration and playstyle altering she forced was so overwhelming that Riot decided to smash her into nonexistence until they could get around to working on her. Again, they didn't do this because she was too strong; they did this because she was too frustrating.
It's probably never going to stop too because instead of waiting for people to find a counter they want instant nerf and instant gratification..
Many of the older champions just straight up don't have counterplay, or it's unreasonably imbalanced. Blitzcrank is a pretty good example of this, because Rocket Grab's potential benefit is so far above its cost that it might as well be undodgeable. If he lands a single good hook lategame, despite missing 400 of them previously, it could singlehandedly (c wut i did thar) win the game for his team. Is he overpowered as a champion? Probably not, but he has some pain points.