rudimentary

basic, simple, uncomplicated

homely, homespun, unsophisticated

early, embryonic, primeval, primordial

backward, underdeveloped, undeveloped

aged, ancient, antediluvian, antiquated, antique, dated, fusty, hoary, musty, obsolete, old, oldfangled, old-fashioned, old-time, out-of-date, outworn, passé, past, quaint, unmodernized

primal, primary, prime, simple

crude, primeval, primitive, primordial, rude, uncomplicated

preliminary, preparatory

crucial, important, key