That is simply untrue. Most basic content will be doable with any combination of talents - I have been running some crazy aoe/ST damage/extreme tankiness/healing builds for my prot pala and doing mid level keys (20s), same with mage, DK and warrior. There are cookie cutters, but there is plenty of fun to be hard to be playing with silly stuff if you don't push too hard. If you are doing hardest content - mythic raids, high m+ there wasn't going to be a choice regardless of what kind of talents there were - community will find out whats the best and that's what you will pick.