There is no need for a theory of determinism if there is no presupposed universal purpose or meaning for existence. any argument that asks for any form of determinism will argue for predestination and given purpose.
Life is just as rich and possible with choices (free will) to be made, including choices of what is the meaning and purpose for each individual.
Granted that one may argue that this gives one a choice for irresponsibility it does not mean one will choose it. There are so many more reasons to choose responsibility over other choices that one may argue that in general people will choose to something akin to morality or ethics.