And through all that time, people have always complained about the meta. Why? because their favorite champs were shafted and champs they dislike were popular.
I'll take a stab at this.
No, onetricks getting shafted isn't the reason people dislike the constant meta shifts. While that really sucks when it happens to you, most people aren't onetricking anyways, so I think it's a bit more than that.
People dislike the constant meta shifts because they're delivered in the guise of "trying to balance the game" (rather than the change for change's sake, aka "keeping the game fresh" that they actually are). These constant, rather unintuitive changes convey the impression that Riot doesn't actually know how to balance their game. Combine that with long-standing problems remaining long-standing problems for very long periods of time (stuff like the Mordekaiser Bug Book, the League of Ardent Censer, "-5 ad lul" etc) after much outrage.. and yeah.
There's no confidence that the people in charge know what they're doing.
I can't blame people for disliking change in something that's marketed primarily as an esport. Name any other sport where if you take a 3-6 month break, vast swathes of your game knowledge are incorrect.