To preface, I have not read the books and solely rely on the show's portrayal of the characters, which as I understand deviates from that of the books'. The first couple of times I watched the show were when seasons 1 & 2 dropped. I was working a soul-crushing job at that time and did not have the mental capacity or energy to fully analyze the characters and their respective arcs. But now that I'm in a better place in life, I could truly pay attention to the details of the plot and it's like a light bulb went on! When you watch the show without truly digesting it, it's so easy to view the characters in a black and white manner. But this time around I was able to understand a lot more of the nuance surrounding these characters - especially Alicent.
I now see her as a victim of her circumstances instead of a mere enabler of her sons. She was manipulated by Otto, Larys, Cole, and other council members, so they can further their own agendas. Alicent was also put in the impossible situation of choosing between her children's survival, which Otto had convinced her would be threatened if Rhaenyra ascends the throne, and doing right by Rhaenyra. Add to that, the fact that she was misled by Visery's deathbed rambling about Aegon the Conquerer's vision. I do not blame her for doing what she did. The only people that are truly to blame are really Otto & Larys, & perhaps Viserys for his horrible parenting skills, lack of foresight/judgement/spine.