In a way, you could look at it like Mako energy is representative of agency, the state of being in the act of changing your environment.

Any action is by nature a destructive action. It is only by resting that anything is created, regenerated, nurtured.

Mako energy represents the power to take action in the universe around you. You want to light something on fire? Fire materia. You want to heal somebody's wound? (You might say that this is an instance of action being regenerative? An exception, maybe, but you do have to destroy the current state of woundedness in order to generate the state of being healed. Not to mention once you heal him, Cloud is going to do Omnislash.) You can do it! Yeah baby!

So nuclear energy is the fullest extent of that ability we have discovered as of yet in the universe we know. The sun generates thermonuclear reactions regularly, as do all stars of that type. The point is, power must not be taken lightly. Or, as Spider Man would say, "with great power comes great responsibility."