Apparently OP has never heard of queue dodging or vote kicking. Which will absolutely happen when people start taking suboptimal specs into the Duty Finder and start producing suboptimal results. You might want to frame things as "people don't care about fun" but I would answer that few find it fun if they perceive they are carrying people who aren't even trying. And many people will see someone in a suboptimal spec performing suboptimally to not be trying, especially once the best specs are identified and widely followed.

As someone else in this thread said, I would rather devs spend their time class balancing new jobs than specs in the same job.