In all seriousness if The Emperor is so powerful why did he do nothing when Vader picked him up? He seemed rather surprised when Vader turned on him so him continuing to use Force Lightning seemed accidental rather than malicious
His over confidence is his weakness. He didn’t expect Vader to turn on him.
If you just watch the OT it’s easy to assume that the Emperor is just more powerful. When I was a kid and first saw Dooku use lightning it was a big what the fuck moment. Even in TFA you don’t see Kylo Ren use lightning. It shouldn’t be ubiquitous for sith and you certainly shouldn’t be able to deflect it so easy.