There was plenty of room for individual experimentation---it was the players who weren't flexible enough. Before role queue, any particular player could, at the drop of a hat, mid-match, mid-life, switch to another of 21 very different heroes. Hard for a game to get more flexible than that!
But in the end, it seems the players didn't want that, and instead wanted less flexibility for their teammates and the enemy team.
Blaming 5 other people for not understanding to play around 21 other wildly different heroes isn't flexibility in game design. Your are asking 5 other people to play a fundamentally different game than the one they have learned.
You couldn't "individually experiment" because fundamentally you needed team experimentation; you can't play Reinhardt in isolation, and subjecting your team to experimentation on your own whims leads to toxicity.
I think many people who go down the "I should be able to play what I want and people should adapt to me" don't realize they are being selfish in play style in a game like Overwatch.
I mean, it sounds like they were just bad at the game that Overwatch was. I learned to adapt around them, after all. I won't deny it was hard. But it was also very fun and rewarding.
Overwatch is a different, less flexible game now, closer to what I think most people thought Overwatch was, and apparently wanted. It is what it is.
But in the end, it seems the players didn't want that, and instead wanted less flexibility for their teammates and the enemy team.