I don’t know what OP’s RP reason was for ascending Astarion, but there are a few answers here, which made me think some people understand the ascended relationship as a consensual sub-dom dynamic, and it’s just not the story.
I gave a few examples in my post higher up that have nothing to do with a wish to be in a sub/dom relationship (I'd even go so far as to assume that it's the least likely reason for most people who choose that path - not saying there's anything wrong with wanting that kind of relationship, either).
The player character does not know what will happen to Astarion when he does the ritual. For all they know he'd be the same person they fell in love with/befriended, just more powerful (there's even a dialogue option that states exactly that). What we as players know and what our characters know are two wholly different things.
Your explanation is an example of meta-gaming (when you act on information your character doesn't have). We are asking for a solution to let us roleplay our character without the writer dictating what our characters' intentions were. No one is asking for them to rewrite Astarion's narrative.
I understad that not everyone is into heavy roleplaying when playing a game like this and a lot of people self-insert (I usually don't), but for us roleplayers a railroading dialogue like this can feel quite frustrating. Especially since it was working out fine up until that pivotal moment.
