The A380, B787 and B777LR are 'horses for courses' and not necessarily competeing in the same market.
23 hours LHR/SYD actually sounds very attractive to frequent travellers whilst low cost pax probably won't object to being herded into an A380, if the price is right.
None of these aircraft are the 'wrong' aircraft, just so long as the market they are aiming for is there in sufficient quantity.