The problem with making all choices "the right choice" is now you stripped that choice of consequences, and meaning with it. You are right in that ideally you want multiple correct answers, but AmiableApkallu is right in that there's got to be consequences and risk involved. Choosing between using a healing resource and MP is a risk because you may need that healing now, but you may not be able to heal later, which as you point out is what Cure vs Cure II is supposed to do, the problem with that though is the amount of free healing from your oGCD and lilies, and MP regen from Lucid, making using Cure vs Cure II a false choice most of the time. Square has removed any risk involved with such decision making, making it a meaningless choice where it's better to use Cure II over Cure. And they've gone further with a large amount of oGCD heals, and frequent damage-neutral heals making Cure II a bad choice over Solace and Tetra.

Energy Drain is an example of risk-reward as, while you want to push your DPS, if it means losing a Broil cast to Adloquium when you could've used Lustrate, then that risk didn't pay off. The choice to use Lustrate or Energy Drain has consequences down the line. This is why many Scholars adamantly defend Energy Drain, because the choice is meaningful, if simple. This is also why people don't fully want your position of making every GCD heal damage neutral down the line, even my redesigns time-gated them in some way so that it rewarded efficient healing choices, rather than spamming Medica back-to-back and getting the same result as the guy who risked a single Medica II.

Even if there's only one "right answer", it's still more meaningful than every choice being the right one, because now there's consequences to making that choice. More meaningful choices doesn't necessarily mean "more optimal choices", although you can have that too, but more often than not, it's about making riskier choices for better rewards. A melee that greeds one extra GCD vs the melee that moved out earlier and spams his ranged a bit is a meaningful choice, the consequences being either more damage while potentially getting hit, or less damage with the guarantee of not getting hurt.