If I understand it right, The final verdict of YK is based on weighing one's merits vs sins and not how hard one davens on Yom Kippur. (Based on Rambam's Hichot Teshuva).
My logic says that the YK day must be dedicated wholly to maximizing one's merits thru performing as many Mitzvot as one can (especially because the work is prohibited, no eating and no procreation it's hard to find Mitzvot. So at least one can be engaged in learning Torah all day long as it is the greatest Mitzvah of them all against all the Mitzvos!).
Instead, we do "nothing Halachicly valuable", besides the [one-time] Viduy (Teshuvah) and Teffila (as for Rambam) (no Tzedaka on YK, sorry).
Acc. to Rambam Teshuva definitely helps to win the case on YK, but this is exactly what seems illogical to me, how talks can be more beneficial when judging a person than good deeds?
The question is how davening on YK is more important than engaging in Mitzvot and Torah learning?
NB: Do you think opening a Kolel "Yom Kippur Torah" for those who can't daven for 6 hours straight is a viable option?