I stopped watching LCS when mains became 'whatever is strong in this meta.' That was the point where unparalleled mechanical ability with a players favourite champion was made redundant by lesser knowledge of a broken champions kit, and Riot encouraged that behaviour.
I understand why players do it, they want their cash prize, though it became a game of 'who picks Fiora/Morgana/Elise/Rengar/<insert whoever has been dominant in any season> first?' rather than the surprise token, fan favourite pick.
DOTA's pro scene, on the other hand, allows more room for players to pick whatever they want. It's more unexpected, unpredictable and that makes it more fun to watch. The meta is solid and doesn't morph into something completely different on a few rounds of nerfs, and thus you're allowed more freedom to experiment around it.
Riot have entered this habit of balancing their game by nerfing the strongest champions, and it's a bad habit to fall in to. The meta becomes unstable, players default to the stronger champions as their safety net and you enter this vicious cycle that effects us, the viewers. To counteract the mess they've created, they need to start buffing other champions to balance their game for them.
We saw this when ADC got their itemization changes, and saw the rise of armour scaling champions like Rammus and Malphite. If things were left as they were, the meta would've balanced out on its own. Less people would play ADC in every role, Rammus' and Malphite's tyranny would die out and you create a level playing field.
Instead, with Riot's infinite wisdom, Rammus and Malphite became the standout champions and received a few hits to curve their win rate and the ADC meta continued unchecked. What happened? The rise of assassins, and the assassin vs ADC meta we're lumped with now. Who can burst who down first? Boring to play, boring to watch.