Rotations are just one of many ways that armchair quarterbacks like to pat themselves on the back as if they know better and have the formula for success.
Or, in other words, the OP is clearly clueless and is simply a Brad Stevens groupie? Or does your claim only apply when people bring up rotations to criticize the coach?
Same thing. To be fair, there may be legitimately bad decisions. If Ainge and Doc and decide to draft JR Giddens earlier than anyone expects, they can also believe in players on the team that they shouldn't.
But the second guessing we see in sports discussions are surreal. A bunch of dudes watching the game on TV and claiming to have all the answers. When one of their 10 complaints pans out, they yell "I told you so" and hope we forget the other 9 things they complained about where they were wrong. They complain about minutia of decisions that obviously can't be redone another way since we can't go back in time, so they are safe from being proven wrong.
Small decisions are given an exaggerated importance as people rail against minor choices instead of realizing that teams lose, players miss shots, and you will often fail despite making the correct choice.
A lot of coaching criticism is like if I say I will give you $100 if you correctly guess whether a die will land on a 1 or on a number between 2-6. If you choose the 1 instead of choosing 2-6, you would be an idiot. 2-6 is the proper guess. If you picked 1 and a 1 was rolled, you would still be an idiot for making a 17% choice instead of an 83% choice. Conversely, if you picked 2-6 and a 1 was rolled, you still made the right choice.
Now imagine a person who doesn't understand that you make decisions based on expectations, not based on knowing the future. They would not be wise enough to understand that the decision that leads to success 90% of the time is still usually the correct move in the 10% where you fail. If you have Ray Allen take you technical free throw, it is the right move whether he makes it or not.
I am not saying that coaches don't make mistakes. Even the best talent evaluators get it wrong at times. But it gets ridiculous when fans go ballistic over these things due to the delusion that they have some sure knowledge about the situation. Express disagreement about the relative values of players on the court, but some people pretend to have some authoritative insights about what would have happened if a different decision was made.