I would rather be OTD then think that Judaism is a class system.
Of course it is. From the Mishna in Keddushin:
?,? ???? ?????? ??? ????–?????, ????, ??????, ????, ???, ??????, ?????, ?????, ?????, ??????. ????? ???? ???????, ?????? ???? ?? ???. ???? ?????? ???? ??? ??????, ?????? ???? ?? ???. ??? ?????? ????? ????? ????? ?????, ?????? ???? ?? ???.
That’s not to say one can not rise above their caste via becoming a Talmid Chacham (similar to a serf joining the priesthood in the middle ages), but it certainly exists in Halacha.