If you disagree with my choice of words and think you know of some that better describe what I mean then you may give a suggestion.
Some determinism is true for stream entrants e.g Attainment of nibbana is guaranteed within 7 lives and definitely within 7 lives etc. Based on conditions of insight etc. So why not for others who aren't stream entrants?
If some determinism is not true then even if there is diligent striving I strive I might end up suffering severely in the next life and even more so than somebody who hasn't even an interest in the Buddha due to "free will" and forgetfulness. In fact all my striving might end up being completely forgotten and eradicated and I might end up being extremely ignorant forever and suffering forever (due to "free will"), whereas someone who had no interest in the Buddha and never does might end up suffering less overall due to "free will".
Imo it seems to undermine the whole idea of kamma and ends up simply being chaotic and random, if specific conditions don't produce specific results.
If you say "it was the person's free will" well then why didn't the kamma and insight from the practice in the past life help the person in the present life not become forgetful or ignorant? Why would a person choose to be severely ignorant besides out of ignorance? Why would a person who is at least somewhat insightful "choose" to go back to ignorance whereas a person who isn't interested in wisdom, wouldn't? Random increase in ignorance, forgetfulness?
Then it's as if for non-stream entrants there is not free will, control or determinism and instead all decisions are simply chosen due to random arising of ignorance.
(It's not my intention to make people delusional and overconfident, but I am interested in this because it seems like it would still be beneficial if one could determine whether a being can be destined for nibbana more than 7 lives beforehand. Maybe one can't be destined for nibbana more than 7 lives beforehand. Maybe it's an unanswerable question. Maybe it would provide a more complete understanding of reality and have various benefits. I don't know)