Part of my problem with it is 1) the implications and 2) ignores the Taoist roots
For 1, the implications of the Dark Side being a side instead of a corruption makes the Star Wars universe… suckier. Because throughout the movies, TV show, and all other stuff, the Dark Side is presented as evil, corrupting, and damaging. Anakin goes off the walls when he falls. Dooku aids in the destruction of the Republic and spread of corruption. Palpatine is manipulative. Say what you want, but all presented Dark Siders are perfectly fine with murder and mass slaughter. Which, as a corruption, makes sense. But as a legitimate, and necessary, side of the Force?
That means that balance in the Force requires a degree of mass slaughter and murder. Which makes balance kind of evil. And this ties into the weird dummying down of Taoism.
(Disclaimer: I am no expert on Taoism and Eastern philosophy, so if someone who is wants to comment I am fine.)
Now, I will not deny that Star Wars has always had Christian themes in it, from the virgin birth to Luke’s redeeming of his father. But those aren’t the only themes. The Jedi have a ton of Eastern influences, from the very name ‘Jedi’. The Force is very Taoist in nature. And in Taoism, it’s not a balance of good and evil. It’s a balance of life and death, chaos and order, with imbalance resulting in evil. You need to accept that death is part of life. You don’t need to accept murder and mass slaughter.
Except… balance is apparently between murder and not murder now.
Having a Light Side, and making the Dark Side equal to it feels like a shitty retcon. And it makes the story worse for it in my opinion. I get graying morality, and letting the Jedi make mistakes and have issues. But turning it from an Order that let politics warp their spiritual beliefs into a group that was clearly wrong about the whole basis of their theology from the beginning where they preached balance by not being balanced feels like it dummies down the story and makes things worse.
(Also, the Light/Dark thing seems to arise out of the need to make flawed good guys become bad guys because… good guys apparently need to be perfect now)
I would also add that it is a deliberate misread of both the OT and the PT in terms of acting. I can get on board with the idea that suppressing one’s feelings is ultimately a terrible thing – I do think that much of Anakin’s arc relates to the idea that he is caught in a cycle of anger and guilt about the very act of feeling. It’s not doctrine, of course, but it is an end result of his interpretation of doctrine and the effects of doctrine on his life, re: attachments. But, nonetheless, Anakin is permitted to feel anger. He is allowed to feel joy. He is allowed to fear a whole spectrum of feelings. He is then supposed to process those feelings and, if they are negative, let them go. The fact that he is incapable of doing that doesn’t in any way prove that such a process is wrongheaded, impossible in general, or contributing to evil in this universe.
Do we see Luke express joy post-training? Yes. Do we see Obi-Wan express joy? I’d argue yes. We see compassion and love from both of them, neither in defiance of doctrine or the apparent balance of the Force. To say they are actively contributing to the imbalance of the Force requires a retrospective misreading of the script and acting in the first six saga movies, to say no, actually, they were emotionless. Or that those moments of emotions were violations, moments in which they were bad Jedi.
So, the Light Side does not forbid emotions. The Jedi encourage healthy processing of emotions. Exactly what is the Dark Side contributing? Oh right. Murder.