At least in the case of Overwatch, role queue feels more like an attempt to assure a minimum level of viability for each team and less like an authoritarian approach to controlling how the game is played.
I'm a Lisp guy, so you can probably guess my opinions on whether it's "worth it" or not to aim for The Right Thing. And one thing I've found in my career is that the teams and individuals that make the best use of Lisp are fairly disciplined about it---they care a lot about functional purity, documentation, interopability, etc.
In other words, they're still operating under restrictions, but they're self-imposed rather than incidental. This foundation of order lets them do crazier things on top of it.
Reducing variance in one's play is the equivalent of writing code without side-effects---it's the fundamental principle of playing nicely with others in its respective domain.
Just as this is best achieved by developer education and discipline in the programming sphere, there needs to be a player ethic of reducing variance (which is why I'm glad to hear about Dallas). And without that, the problem will persist, showing its face in one form or another.
MMR accuracy is probably true, but sheesh, only in a Goodheart's Law kind of way. If it was inaccurate before, that suggests a problem with the statistic, not the game! In a complex game like OW, MMR was always going to be most accurate when applied to teams rather than individuals.
The message a role queue sends is, "Ignore the problems around you and focus on only providing one part of the team's solution" instead of, "Do whatever you can to help the team win." You can't pick up someone else's slack, you can't play unique/innovative styles, you can't adapt to new strategies; it cuts off a huge creative aspect the game used to have.
It's a terrible lesson to teach children.
To apply your reasoning above, removing that ability was a "short term" (rules based) solution to a "long term" problem (balancing the hero roster to make duplicate heroes work in a competitive environment)
With a role queue, you are now unable to solve certain categories of problems your team may have. No one character in Overwatch can exclusively solve a category of problems, so being unable to swap to a specific character isn't nearly as prohibitive.