The fact that earth benders are just able to imbue the earth they bend with shitloads of energy is so ridiculous. The original show explained in good detail how firebenders get the energy to spontaneously generate fire: Breathing acts as a catalyst for their internal energies to circulate like a blast furnace, which lets them expel that energy as fire. Lightning bending is a far more complex technique based on separating positive and negative energies, then collapsing them together in the same way that lightning is generated by positive and negative particles in the air slamming against each other. Earth benders meanwhile move the earth with mentality and stubbornness, they compel the earth to move through being solid and forceful, there's very little artistry to it, hence why tiny delicate details like Toph's recreation of Ba Singh Se is wayyyy more impressive for her skills than even something insane like holding up the entire library. Lavabending just being "Oh yeah so if an earth bender has a firebending parent, their genes mix together and lets them lavabend" is so uncreative and misunderstands bending fundamentally. It treats bending like it's magical genetics instead of a spiritual aspect of the universe.