So, now you're saying these fire mages that everyone played was only in MC? This I can probably agree with, but I hope you can see why I have problems with your original statement. They could have figured out Onyxia was fire immune without a DPS meter... Their "Path" to get there would have been the floating combat text saying Immune. For what it's worth, DPS meters were a thing since before Molten Core was cleared. See here for a video of world first Rag with a DPS meter in plain view: https://www.method.gg/video/Br1hXGXJ7Tg. I did a cursory look at the videos and didn't see a single fireball on any encounter until Naxx. Even in the AQ40 clears were frostbolts which lines up with my memory. Admittedly it's a small sample size, but it's the videos the entire WoW community was watching and emulating.
Stepping away from WoW and your revisionist history...
I believe I understand your point. You think by adding blinders to the players that they will feel more inclined to confer with the community at large in order to determine the best route for performance. This community outreach, in your vision, will create a rich community for the game. Right?
If so, this sort of community interaction still happens on the regular; DPS meter or not. Whether we give the player endless tools or no tools, there will be a subset of players that will go to the forums to ask for guidance, and the inverse is true as well. So in plain words, I disagree.
On an aside, it's odd that somebody with such a lousy attitude wants more community interaction. Misguided principles.