all the effort you put into those achievements is also pre-determined, i.e. that achievement is still unattainable without that effort

Well of course, but the existence of the effort is empty and devoid of "meaning" (whatever "meaning" means). Like, I don't have the words to express this. Yeah, med school is exhausting (so I hear). Not to mention residency, which, like working under a chef, is literal hell, with lots of abusive practices. Like, I hear about those pains, but I don't think their existence makes achieving doctorhood or chefhood more "meaningful". I'm not denying that the suffering was painful for you, I just wish those crappy abusive practices would stop.

There's no way you genuinely believe this.

There is. It's called being a chronic failure. I have basically no achievements to speak of. My whole childhood, I was taught to expect a lot of myself. But also, during the same childhood, I failed nonstop. Not at everything, but it was never like "Oh you failed at this but then you succeeded later". I was always bad at the subjects I was bad at. And I was always good at the subjects I was good at. Coincidentally, those were the subjects that my parents made me do at home. They imported math textbooks from China, and I'd be obliged to do them.

do you have an inescapable feeling of meaninglessness as you come closer to certainty that you'll succeed? Of course not.

Isn't that just called depression?

Anyways, it should be clear by now why I find determinism so attractive. It explains my failures. It explains my mom's abusiveness (boy howdy do I have stories about how my maternal grandmother treated my mom like ass. She was the middle sibling to boot lol, talk about stereotypes). My mom, as I grew into adolescence, would occasionally begin a phrase with "I know you hate me, but [...]" and it's like, with all the stories she's told me about her own abused childhood, I get it. I understood, at that moment, that blame isn't a simple thing. And as I came into my own failures after 18 years old, I also felt the same thing about myself.