Not being able to change Venom Draught choice is absurd

Having to know early on in the campaign exactly how your endgame character is going to be, down to every minute details is nonsenical and very boring. But here we are.

I was struggling with mana so chose mana regen in the campaign. Now, 50 hours later, I am blood magic, which means I have no mana. I also have no charm slots (Shaman) so ele ailment threshold is HUGE for me, this is one of the other options. So now I am stuck with mana regen that does nothing and I am missing 30% ele threshold, which is huge for me.

Am I really expected to just abandon this character and start again just to change this one thing? It's crazy. Why do GGG keep making these same mistakes over and over again? It's like when we couldn't change ascendancies, or when we couldn't change bandit rewards in poe one. It has no positive impact on the game.

The only solution currently is to never run this campaign quest until you are level 95 and utterly certain your character will not change any further, is this what they intended? I doubt it.

Same issue with the seven pillars.