Man i've been playing adcs since 2010. And except Lucian and MF no one ever built BC,you sure as hell didnt see Vayne,Twitch,Tristana or Cait with it,steraks/maw combination was usually used by Graves who is now jungle,like i said,whoever built that didn't do any damage to anyone that is full tank.
I dont want to be that guy to say this but,and its a huge but,youre literally bronze 4,its not that im saying you're bad or something,but in low elos anything goes,hell,i bet teemo and yi are gods and no one knows what to do against Vayne..You get to plat/dia,and things change a lot,you get a tank or two,and a support that are all there to keep the adc alive and soak up the damage,if you're full build and waste 2 slots for Sterak/Maw instead of BT and LDR you're getting outdpsed,it doesn't matter how tanky you are if you are not getting hit,on the other hand that full build enemy Cait or whatever was popular then is shredding your own tank,ripping him to pieces,and he still cant kill her cause she heals from BT,so yeah,going steraks and maw was fun on some adcs maybe so they cant get bursted and can 1v1 better,but that build has never seen the light of any competitive play