I'm not normally a fan of winrates, but they demonstrate the point pretty well:
That's about a tenth of the champion pool, and I'm sure someone is going to point out people I missed. These champs range from sub-par to nearly unplayable without team cooridnation (which you won't be able to find in solo queue, and the worst part is that a fair few of them (sejuani, Galio, Ryze, Maokai, Zac, Gragas, Gangplank, Karma) are sitting in this position because of their VGU/reworks.
Having an underpowered champion is just as gamebreaking as having an over powered one. More needs to be done to support regular players for "pro-centric" champs.