I don't think the lore dump was necessarily bad. But I think that stories should try to not meander.
TADC finale spoilers ahead
The way I see Jax, you can really do only a few things in the finale as it is currently structured:
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Mostly the same, but she de-abstracts/is on the path to doing so after spending half the runtime on emotionally saving her.
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Have the major flashback, then abstract her, putting her in the current "nigh unsaveable state"
In the former case, Jax (alongside Caine), would have to actively earn back the group's trust, because you're right, she's been quite hurtful. But in essence, beyond the moral implications, the narrative structure itself leaves something to be desired in this regard.