No, the burden of proof is one the one saying that X is a viable approach. You're asking people to prove a negative. Here's a thought: we don't need fission no

No, the burden of proof is one the one saying that X is a viable approach. You're asking people to prove a negative. Here's a thought: we don't need fission nor renewables nor storage. Fusion will give us unlimited cheap energy! Now you have to refute every possible implementation of fusion energy - even methods we haven't built or tested - otherwise you're lying. Step up and do your job refuting all possible implementations of fusion! This is the kind of logic you're making with energy storage, and it's faulty logic. If someone wants to claim the viability of fusion, they actually have to deliver a working fusion reactor and at a viable cost. It's not the burden of other people to disprove every possible implementation of fusion.